0001437749-24-009815 | 10-K | XBRL Viewer

Note 11 - Income Taxes

12 Months Ended

Dec. 31, 2023

11. Income Taxes

Income (loss) before income taxes (in thousands):

	Year Ended December 31,
	2023			2022
Domestic	$	(42,210	)	$	(58,505	)
Foreign		—			—
	$	(42,210	)	$	(58,505	)

The components of the provision for income taxes are as follows (in thousands):

	December 31,
	2023		2022
Current
Federal	$	—	$	—
State		—		3
Foreign		—		—
Total current		—		3

Deferred
Federal		—		—
State		—		—
Foreign		—		—
Total deferred		—		—

Total provision for income taxes	$	—	$	3

State income taxes are immaterial in amount and therefore have not been recorded in the Consolidated Statements of Operations and Comprehensive Loss for the years ended December 31, 2023 and 2022.

The provision for income taxes differs from the amount estimated by applying the statutory federal income tax rate to income (loss) before taxes as follows:

	*Year Ended December 31,*
	*2023*			*2022*
Federal tax at statutory rate		21.0	%		21.0	%
State tax at statutory rate		—			8.4
Research and development credits		3.7			0.9
Return to provision		2.6			—
Change in valuation allowance		(19.1	)		(18.4	)
Deferred adjustment		(1.6	)		(5.3	)
Change in tax rate		(5.8	)		—
Uncertain tax position		—			(5.7	)
Other		(0.8	)		(0.9	)
Provision for income taxes		—	%		—	%

Deferred income taxes reflect the impact of carryforwards and temporary differences between the amounts of assets and liabilities for financial reporting purposes and such amounts as measured by tax laws. The carryforwards and temporary differences, which give rise to a significant portion of the Company’s deferred tax asset (liability) as of December 31, 2023 and 2022, are as follows (in thousands):

	*December 31,*
	*2023*			*2022*
Deferred tax assets
Accruals	$	1,502		$	3,404
Net operating loss carryforwards		61,072			56,447
Tax credit carryforwards		9,815			7,111
Stock-based compensation		7,704			8,784
R&D capitalization		7,384			3,810
Lease liability		1,920			2,948
Fixed assets		7			—
Intangibles		99			—
Gross deferred tax assets		89,503			82,504
Valuation allowance		(87,853	)		(79,779	)
Total deferred tax assets		1,650			2,725

Deferred tax liabilities
Intangibles		—			(117	)
Right-of-use asset		(1,650	)		(2,593	)
Fixed assets		—			(15	)
Total deferred tax liabilities		(1,650	)		(2,725	)

Net deferred tax assets/(liabilities)	$	—		$	—

The Company’s unrecognized tax benefits as of December 31, 2023 and 2022 were $10.2 million and $8.9 million, respectively. If recognized, none of the unrecognized tax benefits would impact income tax expense to the extent that the Company continues to maintain a full valuation allowance against its deferred tax assets.

A reconciliation of the beginning and ending amounts of unrecognized tax benefit is as follows (in thousands):

	December 31,
	2023			2022
Unrecognized tax benefits at beginning of year	$	8,925		$	5,140
Increases related to current year tax positions		1,575			2,055
Increases related to prior year tax positions		1,129			1,730
Decreases related to prior year tax positions		(1,459	)		—
Unrecognized tax benefits at end of year	$	10,170		$	8,925

The Company’s policy is to recognize interest and penalties related to income taxes as components of interest expense and other expense, respectively. The Company did not accrue interest and penalties related to unrecognized tax benefits as of December 31, 2023 and does not anticipate any significant change within twelve months of this reporting date.

The Company’s valuation allowance increased by $8.1 million in the year ended December 31, 2023 and increased by $10.8 million in the year ended December 31, 2022.

As of December 31, 2023, the Company had federal and state net operating loss (“NOL”) carryforwards of $222.0 million and $204.4 million, respectively, which begin to expire in 2034. Of the total federal NOL carryforward of $222.0 million, approximately $196.4 million is carried forward indefinitely but is limited to 80% of the taxable income.

As of December 31, 2023, the Company had approximately $8.6 million and $8.1 million of U.S. federal and California research and development (“R&D”) credits, respectively. The federal R&D credits begin to expire in 2035 and the California R&D credits have an indefinite carryforward period.

The Company is subject to taxation in the United States for Federal and for State, within various states in which the Company operates. All jurisdictions and tax years currently remain open for IRS and state taxing authorities’ examination. As of December 31, 2023, the Company was not under examination by the Internal Revenue Service or any state tax jurisdiction.

Internal Revenue Code Section 382 ownership change generally occurs if one or more stockholders or groups of stockholders who own at least 5% of our stock increase their ownership by more than 50 percentage points over their lowest ownership percentage within a rolling three-year period. Similar rules may apply under state tax laws. The Company is not aware of any ownership changes in this financial period ending on December 31, 2023.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

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+ Details

Note 13 - Commitments and Contingencies - Information Related to Right-of-use Assets and Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating right-of-use assets	$ 7,256	$ 8,062
Lease liability, current	1,058	896
Lease liability, less current portion	8,086	9,144
Total lease liabilities	9,144	10,040
Cash paid for operating lease liabilities	1,845	$ 1,806
2024	1,910
2025	1,977
2026	2,046
2027	2,117
2028	2,191
Thereafter	1,883
Total lease payments	12,124
Less imputed interest	$ (2,980)
Weighted-average remaining lease term (Year)	5 years 9 months 29 days
Weighted-average discount rate	10.00%

Note 11 - Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]

	Year Ended December 31,
	2023			2022
Domestic	$	(42,210	)	$	(58,505	)
Foreign		—			—
	$	(42,210	)	$	(58,505	)

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

	December 31,
	2023		2022
Current
Federal	$	—	$	—
State		—		3
Foreign		—		—
Total current		—		3

Deferred
Federal		—		—
State		—		—
Foreign		—		—
Total deferred		—		—

Total provision for income taxes	$	—	$	3

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

	*Year Ended December 31,*
	*2023*			*2022*
Federal tax at statutory rate		21.0	%		21.0	%
State tax at statutory rate		—			8.4
Research and development credits		3.7			0.9
Return to provision		2.6			—
Change in valuation allowance		(19.1	)		(18.4	)
Deferred adjustment		(1.6	)		(5.3	)
Change in tax rate		(5.8	)		—
Uncertain tax position		—			(5.7	)
Other		(0.8	)		(0.9	)
Provision for income taxes		—	%		—	%

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

	*December 31,*
	*2023*			*2022*
Deferred tax assets
Accruals	$	1,502		$	3,404
Net operating loss carryforwards		61,072			56,447
Tax credit carryforwards		9,815			7,111
Stock-based compensation		7,704			8,784
R&D capitalization		7,384			3,810
Lease liability		1,920			2,948
Fixed assets		7			—
Intangibles		99			—
Gross deferred tax assets		89,503			82,504
Valuation allowance		(87,853	)		(79,779	)
Total deferred tax assets		1,650			2,725

Deferred tax liabilities
Intangibles		—			(117	)
Right-of-use asset		(1,650	)		(2,593	)
Fixed assets		—			(15	)
Total deferred tax liabilities		(1,650	)		(2,725	)

Net deferred tax assets/(liabilities)	$	—		$	—

Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]

	December 31,
	2023			2022
Unrecognized tax benefits at beginning of year	$	8,925		$	5,140
Increases related to current year tax positions		1,575			2,055
Increases related to prior year tax positions		1,129			1,730
Decreases related to prior year tax positions		(1,459	)		—
Unrecognized tax benefits at end of year	$	10,170		$	8,925

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 44,365	$ 61,139
Prepaid expenses and other current assets	963	1,008
Total current assets	45,328	62,147
Property and equipment, net	1,528	1,961
Intangible assets, net	1,886	2,551
Goodwill	2,791	2,791
Right-of-use assets	7,256	8,062
Other assets	365	365
Total assets	59,154	77,877
Current liabilities:
Accounts payable	1,836	1,573
Accrued expenses	3,814	2,595
Lease liability, current	1,058	896
Related party note payable, current	0	917
Total current liabilities	6,708	5,981
Lease liability, less current portion	8,086	9,144
Related party note payable, less current	0	65,000
Total liabilities	14,794	80,125
Commitments and contingencies (Note 13)
Stockholders’ equity:
Preferred stock, $0.001 par value; authorized – 50,000 shares; no shares issued and outstanding	0	0
Common stock, $0.001 par value; authorized – 500,000 shares; issued and outstanding – 55,144 shares and 37,235 shares at December 31, 2023 and 2022, respectively	55	37
Additional paid-in capital	381,220	292,420
Accumulated other comprehensive income (loss)	0	0
Accumulated deficit	(336,915)	(294,705)
Total stockholders’ equity (deficit)	44,360	(2,248)
Total liabilities and stockholders’ equity	$ 59,154	$ 77,877

Consolidated Statements of Stockholders' Equity (Deficit) (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Rights Offering [Member]
Issuance cost		$ 136
Private Placement [Member]
Issuance cost	$ 6
Shares Issued Upon Warrants Exercised [Member]
Issuance cost	$ 9

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Time-based Option Activity (Details) - Time-based Options [Member] - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Options balances, number of shares (in shares)	4,730,394
Options balances, weighted average exercise price (in dollars per share)	$ 12.95
Options balances, weighted average remaining life (Year)	7 years 25 days	6 years 1 month 28 days
Options granted, number of shares (in shares)	2,390,386
Options granted, weighted average exercise price (in dollars per share)	$ 4.7
Options exercised, number of shares (in shares)	(301,254)
Options exercised, weighted average exercise price (in dollars per share)	$ 3.89
Options canceled, number of shares (in shares)	(262,994)
Options canceled, weighted average exercise price (in dollars per share)	$ 6.06
Options expired, number of shares (in shares)	(414,626)
Options expired, weighted average exercise price (in dollars per share)	$ 13.01
Options balances, number of shares (in shares)	6,141,906	4,730,394
Options balances, weighted average exercise price (in dollars per share)	$ 10.48	$ 12.95
Options exercisable, number of shares (in shares)	3,390,035
Options exercisable, weighted average exercise price (in dollars per share)	$ 14.47
Options exercisable, weighted average remaining life (Year)	5 years 3 months 10 days

Note 12 - Related Party Transactions

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

12. Related Party Transactions

In May 2022, the Company determined not to renew its annual director and officer liability insurance policy due to disproportionately high premiums quoted by insurance companies. Instead, on May 31, 2022, the Company and Robert W. Duggan, majority stockholder and Executive Chairman, entered into a letter agreement (the “Letter Agreement”) pursuant to which Mr. Duggan agreed with the Company to personally provide indemnity coverage for a one-year period, and he agreed to deposit cash and/or marketable securities into a third-party escrow, as security for these obligations, if requested by the Company. On May 31, 2023, the last day of the one-year period, the Company paid Mr. Duggan a fee of $1.0 million in consideration of the obligations set forth in the Letter Agreement. As of December 31, 2023, there were no additional amounts owed to Mr. Duggan under the Letter Agreement.

On June 9, 2022, the Company completed the 2022 Rights Offering resulting in the sale of 7,317,072 Units, at a price of $2.05 per Unit, with each Unit consisting of one share of the Company’s common stock, par value $0.001 per share, and one 2022 Rights Offering Warrant to purchase one share of common stock at a price of $2.05 per share. Robert W. Duggan, the Company’s majority stockholder and Executive Chairman, purchased approximately 56% of the shares offered through the 2022 Rights Offering.

On September 20, 2022, the Company and Robert W. Duggan, the Company's majority stockholder and Executive Chairman, entered into the 2022 Loan Agreement in connection with Mr. Duggan lending the principal sum of $65.0 million to the Company. On April 30, 2023, the Company entered into a Securities Purchase Agreement with Mr. Duggan, pursuant to which the Company agreed to issue and sell to Mr. Duggan 10,022,937 shares of the Company’s common stock, par value $0.001 per share, in a Private Placement, at a price per share of $6.51. These shares were paid for through the cancellation of the amounts then owed by the Company under the 2022 Loan Agreement, the principal sum of $65.0 million and all accrued and unpaid interest outstanding, which totaled approximately $0.2 million as of April 30, 2023. Upon closing of the Private Placement and satisfaction of the outstanding debt, the 2022 Loan Agreement terminated, without early termination fees or penalties being owed by the Company. No additional amounts are owed to Mr. Duggan under the 2022 Loan Agreement. See Note 13 for further details.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

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+ Details

Note 12 - Related Party Transactions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended
	May 31, 2023	Apr. 30, 2023	Sep. 20, 2022	Jun. 09, 2022	Mar. 31, 2023	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Accrued Liabilities, Current						$ 3,814		$ 2,595
Common Stock, Par or Stated Value Per Share (in dollars per share)						$ 0.001		$ 0.001
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)						$ 0		$ 2.05
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness		$ 65,000
Interest Payable		$ 200
Rights Offering [Member]
Equity Offering, Units, Sale of Units (in shares)				7,317,072
Shares Issued, Price Per Share (in dollars per share)				$ 2.05
Number of Shares Per Unit Issued (in shares)				1
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Number of Warrants Per Unit (in shares)				1
Stock Issued During Period, Shares, New Issues (in shares)				7,317,072
Robert W. Duggan [Member] \| Rights Offering [Member]
Equity Offering, Units, Sale of Units (in shares)				7,317,072
Shares Issued, Price Per Share (in dollars per share)				$ 2.05
Number of Shares Per Unit Issued (in shares)				1
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Number of Warrants Per Unit (in shares)				1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)				1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 2.05
Investment Owned, Percent of Net Assets				56.00%
Robert W. Duggan [Member] \| Private Placement [Member]
Shares Issued, Price Per Share (in dollars per share)		$ 6.51
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.001
Stock Issued During Period, Shares, New Issues (in shares)		10,022,937
Letter Agreement [Member] \| Robert W. Duggan [Member]
Directors and Officers Liability Insurance, Period (Year)					1 year
Related Party Transaction, Amounts of Transaction	$ 1,000		$ 65,000
Accrued Liabilities, Current							$ 0

Note 11 - Income Taxes - Reconciliation of Provision for Income Taxes (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Federal tax at statutory rate	21.00%	21.00%
State tax at statutory rate	0.00%	8.40%
Research and development credits	3.70%	0.90%
Return to provision	2.60%	0.00%
Change in valuation allowance	(19.10%)	(18.40%)
Deferred adjustment	(1.60%)	(5.30%)
Change in tax rate	(5.80%)	0.00%
Uncertain tax position	0.00%	(5.70%)
Other	(0.80%)	(0.90%)
Provision for income taxes	0.00%	0.00%

Note 2 - Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Significant Accounting Policies [Text Block]

2. Summary of Significant Accounting Policies

Principles of Consolidation

The accompanying consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities Exchange Commission (the “SEC”). The consolidated financial statements include the financial statements of the Company and its wholly-owned subsidiaries and intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires the Company to make estimates that affect the amounts reported in the financial statements and accompanying notes to the financial statements. Estimates include, but are not limited to, the valuation and recognition of stock-based compensation, inventory valuation, warranty obligations, income taxes, and the useful lives assigned to long-lived assets. The Company evaluates its estimates and assumptions based on historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ materially from these estimates.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents and investments. The Company places its cash equivalents and investments with high credit quality financial institutions and, by policy, limits the amounts invested with any one financial institution or issuer. Deposits held with banks may exceed the amount of insurance provided on such deposits. The Company has not experienced any losses since inception.

Fair Value of Financial Instruments

The Company believes the carrying amounts of its financial instruments, including cash equivalents, prepaid expenses and other current assets, accounts payable and accrued expenses, approximate fair value due to the short-term nature of such instruments.

Cash and Cash Equivalents

The Company invests its cash primarily in money market funds. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.

Property and Equipment

Property and Equipment is recorded at cost and depreciated using the straight-line method over their estimated useful lives, ranging from three to five years. Leasehold improvements are amortized using the straight-line method over the shorter of the lease term or estimated useful life. Upon the sale or retirement of property and equipment, the costs and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss is reflected in operating expenses. Maintenance and repairs are charged to operations as incurred.

Valuation of Inventory

Inventory is stated at lower of cost or net realizable value. The Company establishes the inventory basis by determining the cost based on standard costs approximating the purchase costs on a first-in, first-out basis. Net realizable value is the estimated selling price in the ordinary course of the Company’s business, less reasonably predictable costs of completion, disposal, and transportation. The cost basis of the Company’s inventory will be reduced for any products that are considered excessive or obsolete based upon assumptions about future demand and market conditions. At December 31, 2022, the inventory balance was fully written off due to excessive and obsolete inventory and the Company does not plan to capitalize further inventory in relation to the dermatology market.

Intangible Assets

The Company’s intangible assets consist of acquired patents and licenses, which are amortized over their estimated useful lives of twelve years.

Long-Lived Assets

The Company reviews long-lived assets, consisting of property and equipment and intangible assets, for impairment during each fiscal year or when events or changes in circumstances indicate the carrying value of these assets may exceed their current fair values. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. No impairment losses were incurred during the periods presented.

Goodwill

The Company records goodwill when the consideration paid in a business acquisition exceeds the fair value of the net tangible assets and the identified intangible assets acquired. The Company reviews goodwill for impairment at the reporting unit level at least annually or whenever changes in circumstances indicate that the carrying value of the goodwill may not be recoverable. To date, there has been no impairment of goodwill.

Revenue from Contracts with Customers

The Company recognized revenue at a point in time when it satisfied performance obligations by transferring control of promised goods to its customers. The amount of revenue recognized was equal to the consideration which the Company was entitled to in exchange for the promised goods, excluding any amounts assessed by government authorities for taxes which might have been collected from a customer. Sales contracts often involved the sale and delivery of multiple products, each of which typically represented a separate performance obligation in the contract. While the Company has sold these products on a stand-alone basis at their respective stand-alone selling prices (“SSP”), initial customer contracts primarily involved the bundling of products which were delivered concurrently to the customer. In such instances, the full consideration of the contract was recognized upon shipment of the products. The Company generally required receipt of full payment prior to shipment, however, from time to time, payment terms were extended to customers upon which the Company performed a necessary credit evaluation to ensure future collectability of the outstanding balance. The accounts receivable balance at December 31, 2023 is zero and the Company has therefore not recorded an allowance against the accounts receivable balance. Refer to Note 9 for further details.

Product Warranty

The Company provides a standard warranty on eligible products which provides the customer assurances that the products comply with the agreed-upon specifications. The standard warranty does not provide any services in addition to those assurances. The Company accrued a warranty reserve for products sold based upon the best estimate of the nature, frequency, and costs of future claims. These estimates are inherently uncertain given the short history of sales, and changes to the historical or projected warranty experience may cause material changes to the warranty reserve in the future. During the year ended December 31, 2023, the Company reduced the accrued warranty liability to zero. Based upon the Company's shift in focus, there are a limited number of consoles currently covered under the standard warranty. All inventory has been fully written off, therefore the only incremental costs to fulfill a warranty claim would be shipping costs, which will be immaterial in nature.

Warranty accrual activity consisted of the following (in thousands):

	*Year Ended December 31,*
	*2023*			*2022*
Beginning balance	$	50		$	80
Add: Accruals for warranties issued during the period		—			42
Less: Adjustment for inventory at cost and excessive and obsolete inventory		(50	)		(72	)
Ending balance	$	—		$	50

Stock-Based Compensation

The Company's stock-based compensation programs include stock options and an employee stock purchase program.

The Company periodically issues stock options to officers, directors, employees, and consultants for services rendered. Such issuances vest and expire according to terms established at the issuance date. Stock-based payments to officers, directors and employees, including grants of employee stock options, are recognized in the financial statements based on their grant date fair values, which are estimated using the Black-Scholes option-pricing model. Stock-based compensation expense is charged to operations on a straight-line basis over the vesting period. The Company has granted stock options with both time-based as well as performance-based vesting conditions. For stock awards with performance-based vesting conditions, the Company does not recognize compensation expense until it is probable that the performance-based vesting condition will be achieved. The analysis to determine such probability involves estimates and judgements from management and the estimate of expense may be revised periodically.

The Company has also issued certain stock options with market-based vesting conditions. These vesting conditions relate to the achievement of certain market capitalization targets of the Company. The grant date fair value for these stock options was determined using a Monte Carlo simulation. The expense is recognized over the requisite service period for each tranche of the awards. The requisite service period is the service period derived from the Monte Carlo simulation model. If the market capitalization targets are met sooner than the derived service period, the Company will accelerate the recognition of stock-based compensation expense to reflect the cumulative expense associated with the vested shares. The Monte Carlo simulation requires the Company to make assumptions and judgements about the variables used in the calculation including the expected term, volatility of the Company's common stock, an assumed risk-free interest rate, and cost of equity. The assumptions used in the option-pricing model represent management’s best estimates. If factors change and different assumptions are used, the Company's stock-based compensation expense could be materially different in the future.

See Note 6 for a detailed discussion of the Company’s stock plans and stock-based compensation expense.

Research and Development Costs

Research and development costs consist primarily of compensation costs, fees paid to consultants and outside service providers and organizations (including university research institutes), costs associated with clinical trials, development prototypes and other expenses relating to the acquisition, design, development and testing of the Company’s product candidates, and certain facilities related costs. Research and development costs incurred by the Company are expensed as incurred, unless the achievement of milestones, the completion of contracted work, or other information indicates that a different expensing schedule is more appropriate.

Patent Costs

The Company is the owner of numerous domestic and foreign patents. Due to the significant uncertainty associated with the successful development of one or more commercially viable products based on the Company’s research efforts and any related patent applications, patent costs not related to acquired patents, including patent-related legal fees, filing fees and other costs, including internally generated costs, are expensed as incurred. During both of the years ended December 31, 2023 and 2022, patent costs totaled $0.5 million, respectively. Patent costs are included in general and administrative costs in the consolidated statements of operations and comprehensive loss.

Income Taxes

The Company accounts for income taxes under an asset and liability approach for financial accounting and reporting for income taxes. Accordingly, the Company recognizes deferred tax assets and liabilities for the expected impact of differences between the financial statements and the tax basis of assets and liabilities.

The Company records a valuation allowance to reduce its deferred tax assets to the amount that is more-likely-than-not to be realized. In the event the Company determines that it would be able to realize its deferred tax assets in the future in excess of its recorded amount, an adjustment to the deferred tax assets would be credited to operations in the period such determination was made. Likewise, should the Company determine that it would not be able to realize all or part of its deferred tax assets in the future, an adjustment to the deferred tax assets would be charged to operations in the period such determination was made.

The Company is subject to U.S. federal income taxes and state income taxes in various states. As the Company’s net operating losses have yet to be utilized, previous tax years remain open to examination by federal authorities and other jurisdictions in which the Company currently operates or has operated in the past. The Company is not currently under examination by any tax authority.

The Company accounts for uncertainties in income tax law under a comprehensive model for the financial statement recognition, measurement, presentation and disclosure of uncertain tax positions taken or expected to be taken in income tax returns as prescribed by U.S. GAAP. The tax effects of a position are recognized only if it is more-likely-than-not to be sustained by the taxing authority as of the reporting date. If the tax position is not considered more-likely-than-not to be sustained, then no benefits of the position are recognized. At December 31, 2023 and 2022, the Company had not recorded any liability for uncertain tax positions. The Company includes interest and penalties related to uncertain tax positions as a component of income tax expense.

Comprehensive Loss

The Company displays comprehensive loss, and if applicable its components, as part of the consolidated statements of operations and comprehensive loss. There were no adjustments to comprehensive loss during both of the years ended December 31, 2023 and 2022.

Net Loss per Share

The Company calculates basic net loss per share by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potential dilutive common stock equivalents outstanding during the period. For purposes of this calculation, options to purchase common stock and common stock warrants are considered common stock equivalents. Potential common shares that have an anti-dilutive effect (i.e., those that increase income per share or decrease loss per share) are excluded from the calculation of diluted net loss per share.

The following outstanding stock options, warrants, and RSUs to purchase common stock were excluded from the computation of diluted net loss per share for the periods presented because including them would have had an anti-dilutive effect:

	Year Ended December 31,
	2023		2022
Common stock warrants		—		7,303,832
Common stock options		9,466,036		5,250,696
Total		9,466,036		12,554,528

Segment and Geographical Information

The Company operates in one segment and reports segment information in accordance with ASC 280, Segment Reporting. Management uses one measurement of profitability and does not segregate its business for internal reporting, however in making certain operating decisions and assessing performance, management will additionally review the disaggregated revenue results by product and geography. The Company’s Chief Executive Officer acts as the chief operating decision makers (“CODM”) of the Company. As of December 31, 2023 and 2022, 100% of long-lived assets were in the United States. Revenue is attributed to a geographic region based on the location of the end customer.

See Note 10 for details of revenue by product and geography.

Recent Accounting Pronouncements Not Yet Adopted

In October 2023, the FASB issued ASU 2023-06, Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. This guidance affects a wide variety of topics in the Codification. The effective date for each amendment will be the date on which the removal of the respective related disclosures from Regulation S-X or Regulation S-K becomes effective. Early adoption is prohibited and the amendments in this ASU should be applied prospectively. The Company does not expect the adoption of this standard to have a material impact on the Company’s consolidated financial statements and related disclosures.

In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. The amendments in this ASU require disclosures, on an annual and interim basis, of significant segment expenses that are regularly provided to the CODM, as well as the aggregate amount of other segment items included in the reported measure of segment profit or loss. This ASU requires that a public entity disclose the title and position of the CODM and an explanation of how the CODM uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. Public entities will be required to provide all annual disclosures currently required by Topic 280 in interim periods, and entities with a single reportable segment are required to provide all the disclosures required by the amendments in this ASU and existing segment disclosures in Topic 280. This ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The amendments in this ASU should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures, and does not expect the standard will have a material impact on the Company’s consolidated financial statements and related disclosures.

In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. This ASU requires greater disaggregation of information about a reporting entity's effective tax rate reconciliation as well as information on income taxes paid. This ASU applies to all entities subject to income taxes and is intended to help investors better understand an entity’s exposure to potential changes in jurisdictional tax legislation and assess income tax information that affects cash flow forecasts and capital allocation decisions. This ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted. This ASU should be applied on a prospective basis although retrospective application is permitted. The Company is currently evaluating the impact the adoption of this ASU will have on its consolidated financial statements and related disclosures.

Note 6 - Stockholders' Equity and Stock-based Compensation - Option Assumptions (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Market-based Options [Member]
Expected volatility	90.00%	0.00%
Risk-free interest rate		0.00%
Dividend yield	0.00%	0.00%
Time-based and Performance Options [Member]
Dividend yield	0.00%
Minimum [Member] \| Market-based Options [Member]
Expected term in years (Year)	4 years
Risk-free interest rate	3.40%
Minimum [Member] \| Time-based and Performance Options [Member]
Expected term in years (Year)	5 years	5 years 3 months 18 days
Expected volatility	89.00%	83.00%
Risk-free interest rate	3.70%	1.90%
Maximum [Member] \| Market-based Options [Member]
Expected term in years (Year)	6 years 3 months 18 days
Risk-free interest rate	3.80%
Maximum [Member] \| Time-based and Performance Options [Member]
Expected term in years (Year)	8 years	6 years 9 months 18 days
Expected volatility	95.00%	88.00%
Risk-free interest rate	4.40%	3.20%

Note 7 - Research Grants and Agreements (Details Textual) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	May 31, 2021	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Research and Development Expense			$ 27,797	$ 20,839
Old Dominion University Research Foundation [Member] \| Sponsored Research Agreement SRA [Member]
Research and Development Expense			$ 0	$ 200
Old Dominion University Research Foundation [Member] \| Sponsored Research Agreement SRA [Member] \| Research and Development Arrangement [Member]
Long-Term Purchase Commitment, Amount	$ 300	$ 300

Note 2 - Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive securities (in shares)	9,466,036	12,554,528
Warrant [Member]
Antidilutive securities (in shares)	0	7,303,832
Share-Based Payment Arrangement, Option [Member]
Antidilutive securities (in shares)	9,466,036	5,250,696

Note 2 - Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Product Warranty Liability [Table Text Block]

	*Year Ended December 31,*
	*2023*			*2022*
Beginning balance	$	50		$	80
Add: Accruals for warranties issued during the period		—			42
Less: Adjustment for inventory at cost and excessive and obsolete inventory		(50	)		(72	)
Ending balance	$	—		$	50

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]

	Year Ended December 31,
	2023		2022
Common stock warrants		—		7,303,832
Common stock options		9,466,036		5,250,696
Total		9,466,036		12,554,528

Note 4 - Balance Sheet Components - Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Compensation expense	$ 3,199	$ 1,377
Director and officer liability insurance (Note 12)	0	571
Clinical trial fees and costs	84	64
Professional fees	343	318
Warranty	0	50	$ 80
Other	188	215
Accrued Liabilities, Current	$ 3,814	$ 2,595

Note 17 - Subsequent Events

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Subsequent Events [Text Block]

17. Subsequent Events

In March 2024, the Company received FDA 510(k) clearance for its CellFX nsPFA Percutaneous Electrode System for use in the ablation of soft tissue in percutaneous and intraoperative surgical procedures. Having secured regulatory approval to market and sell the CellFX nsPFA Percutaneous Electrode System in the United States, we have initiated a limited market release, targeting a handful of select accounts.

In March 2024, the Board approved a second amendment to the Company’s Inducement Plan to reserve an additional 2,000,000 shares of the Company’s common stock for issuance pursuant to the Inducement Plan.

Note 3 - Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Fair Value Disclosures [Text Block]

3. Fair Value of Financial Instruments

Fair Value of Financial Instruments

The Company determines the fair value of its financial instruments based on a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three levels:

Level 1 – Observable inputs such as quoted prices in active markets for an identical asset or liability that the Company has the ability to access as of the measurement date. Financial assets and liabilities utilizing Level 1 inputs include money market funds.

Level 2 – Inputs, other than quoted prices included within Level 1, which are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. The Company did not classify any of its investments within Level 2 of the fair value hierarchy.

Level 3 – Unobservable inputs in which there is little or no market data for the asset or liability which requires the reporting entity to develop its own assumptions. The Company did not classify any of its investments within Level 3 of the fair value hierarchy.

The following table sets forth the fair value of the Company’s financial assets measured on a recurring basis (in thousands):

		*December 31, 2023*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	41,184	$	—	$	—	$	41,184
Total assets measured at fair value		$	41,184	$	—	$	—	$	41,184

		*December 31, 2022*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	57,973	$	—	$	—	$	57,973
Total assets measured at fair value		$	57,973	$	—	$	—	$	57,973

During the years ended December 31, 2023 and 2022, the Company did not record impairment charges related to its cash equivalents. During the years ended December 31, 2023 and 2022, the Company did not have any transfers between Level 1, Level 2 or Level 3 of the fair value hierarchy. Additionally, the Company did not have any financial assets and liabilities measured at fair value on a non-recurring basis as of December 31, 2023 or 2022.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Note 4 - Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property and equipment, gross	$ 5,004	$ 4,914
Less: Accumulated depreciation and amortization	(3,476)	(2,953)
Property and equipment, net	1,528	1,961
Leasehold Improvements [Member]
Property and equipment, gross	2,519	2,519
Laboratory Equipment [Member]
Property and equipment, gross	1,247	1,118
Furniture and Fixtures [Member]
Property and equipment, gross	966	966
Software and Software Development Costs [Member]
Property and equipment, gross	272	289
Construction in Progress [Member]
Property and equipment, gross	$ 0	$ 22

Note 6 - Stockholders' Equity and Stock-based Compensation - Stock-based Compensation Expense by Type (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total stock-based compensation expense	$ 7,181	$ 5,191
Time-based Options [Member]
Total stock-based compensation expense	3,827	4,467
Performance-based Options [Member]
Total stock-based compensation expense	1,977	233
Market-based Options [Member]
Total stock-based compensation expense	1,130	0
Employee Stock Purchase Plan Award [Member]
Total stock-based compensation expense	$ 247	$ 491

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Warrants Activity (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Warrants outstanding, number of shares (in shares) \| shares	7,303,832
Warrants outstanding, weighted average exercise price (in dollars per share) \| $ / shares	$ 2.05
Warrants outstanding, weighted average remaining contractual life (Year)	4 years 5 months 4 days
Warrants issued, number of shares (in shares) \| shares	0
Warrants issued, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Warrants exercised, number of shares (in shares) \| shares	(7,237,657)
Warrants exercised (in dollars per share) \| $ / shares	$ 2.05
Warrants Expired/Redeemed, number of shares (in shares) \| shares	(66,175)
Warrants Expired/Redeemed, weighted average exercise price (in dollars per share) \| $ / shares	$ 2.05
Warrants outstanding, number of shares (in shares) \| shares	0
Warrants outstanding, weighted average exercise price (in dollars per share) \| $ / shares	$ 0

Note 6 - Stockholders' Equity and Stock-based Compensation - Stock-based Compensation Expense by Recorded Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total stock-based compensation expense	$ 7,181	$ 5,191
Cost of Sales [Member]
Total stock-based compensation expense	0	217
Research and Development Expense [Member]
Total stock-based compensation expense	3,491	1,563
Selling and Marketing Expense [Member]
Total stock-based compensation expense	0	733
General and Administrative Expense [Member]
Total stock-based compensation expense	$ 3,690	$ 2,678

Note 16 - Supplementary Financial Information

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Quarterly Financial Information [Text Block]

16. Supplementary Financial Information

There are no retrospective changes to the statements of comprehensive income for any of the quarters within the two most recent fiscal years that individually or in the aggregate are material.

Note 11 - Income Taxes - Components of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current
Federal	$ 0	$ 0
State	0	3
Foreign	0	0
Total current	0	3
Deferred
Federal	0	0
State	0	0
Foreign	0	0
Total deferred	0	0
Total provision for income taxes	$ 0	$ 3

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (42,210)	$ (58,505)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	542	690
Amortization of intangible assets	665	665
Stock-based compensation	7,181	5,191
Write-off of excessive and obsolete inventory	0	8,477
Loss on disposal of fixed assets	13	185
Changes in operating assets and liabilities:
Accounts receivable	0	61
Inventory	0	(2,653)
Prepaid expenses and other current assets	(65)	1,164
Other receivables	109	(41)
Right-of-use assets	806	723
Accounts payable	263	(1,304)
Accrued expenses	1,219	(1,794)
Deferred revenue	0	(16)
Lease liabilities	(896)	(774)
Accrued interest on related party note payable	(668)	917
Accrued interest on note payable	0	1
Net cash used in operating activities	(33,041)	(47,013)
Cash flows from investing activities:
Purchases of property and equipment	(121)	(401)
Net cash used in investing activities	(121)	(401)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee stock purchase plan	395	486
Proceeds from exercises of warrants	14,828	26
Proceeds from exercises of stock options	1,171	0
Proceeds from issuance of common stock	0	14,864
Proceeds from issuance of related party note	0	65,000
Issuance cost in relation to related party note extinguishment	(6)	0
Payments made on insurance loan agreement	0	(437)
Net cash provided by financing activities	16,388	79,939
Net (decrease) increase in cash and cash equivalents	(16,774)	32,525
Cash and cash equivalents at beginning of period	61,139	28,614
Cash and cash equivalents at end of period	44,365	61,139
Supplemental disclosure of noncash investing and financing activities:
Principal and accrued interest of related party note settled via issuance of common stock	(65,249)	0
Equipment purchases included in accounts payable and accrued expenses	$ 0	$ (27)

Note 6 - Stockholders' Equity and Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended				6 Months Ended	12 Months Ended
	Apr. 30, 2023	Jan. 01, 2023	Jun. 09, 2022	Mar. 31, 2024	Dec. 31, 2023	May 31, 2021	Nov. 30, 2017	Jun. 15, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2017
Preferred Stock, Shares Authorized (in shares)					50,000,000				50,000,000	50,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001				$ 0.001	$ 0.001
Preferred Stock, Shares Outstanding, Ending Balance (in shares)					0				0	0
Common Stock, Shares Authorized (in shares)					500,000,000				500,000,000	500,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001				$ 0.001	$ 0.001
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)					$ 0				$ 0	$ 2.05
Proceeds from Issuance of Common Stock									$ 0	$ 14,864
Class of Warrant or Right, Exercised During Period (in shares)									7,237,657
Proceeds from Warrant Exercises									$ 14,828	$ 26
Class of Warrant or Right, Outstanding (in shares)					0				0	7,303,832
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount					$ 9,700				$ 9,700
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)									4 years 2 months 8 days
Time-based Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value									$ 900
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value									$ 9,000	$ 2,300
Time-based Options [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage									25.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)									1 year
Performance Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value									$ 2,000	800
Market-based Options [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Intrinsic Value									$ 10,500	$ 0
The 2017 Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)											10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)											1,500,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)		1,200,000			1,375,000					1,188,657
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Number of Shares (in shares)											1,200,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Percent											4.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					231,763				231,763
The 2017 Inducement Equity Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)							10 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)							1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)						1,000,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					1,249,126				1,249,126
The 2017 Inducement Equity Incentive Plan [Member] \| Subsequent Event [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)				2,000,000
The 2017 Inducement Equity Incentive Plan [Member] \| Share-Based Payment Arrangement, Tranche One [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage							25.00%
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)							1 year
The 2017 Inducement Equity Incentive Plan [Member] \| Share-Based Payment Arrangement, Option [Member] \| Maximum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period (Year)							10 years
The 2017 Employee Stock Purchase Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)											250,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Number of Shares (in shares)											450,000
Increase in Shares Available for Issuance, Threshold of Common Stock Outstanding, Percent											1.50%
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Available for Grant (in shares)					113,318				113,318
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)									347,681	188,097
Rights Offering Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)			1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 2.05		$ 2.05				$ 2.05
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)					7,317,072				7,317,072
Class of Warrants or Rights, Redemption Price Per Share (in dollars per share)					$ 0.01				$ 0.01
Class of Warrant or Right, Period of Written Notice for Exercise (Day)									30 days
Class of Warrant or Right, Percentage Required for Redemption					200.00%				200.00%
Class of Warrant or Right, Exercise, Consecutive Trading Days (Day)									20 days
Class of Warrant or Right, Exercised During Period (in shares)								7,250,897	66,175
Proceeds from Warrant Exercises								$ 14,900
Class of Warrant or Right, Outstanding (in shares)					0				0
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness	$ 65,000
Private Placement [Member] \| Robert W. Duggan [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.001
Stock Issued During Period, Shares, New Issues (in shares)	10,022,937
Shares Issued, Price Per Share (in dollars per share)	$ 6.51
Rights Offering [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)			$ 0.001
Stock Issued During Period, Shares, New Issues (in shares)			7,317,072
Shares Issued, Price Per Share (in dollars per share)			$ 2.05
Equity Offering, Units, Sale of Units (in shares)			7,317,072
Number of Shares Per Unit Issued (in shares)			1
Number of Warrants Per Unit (in shares)			1
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)			7,317,072
Proceeds from Issuance of Common Stock			$ 15,000
Class of Warrants or Rights, Redemption Price Per Share (in dollars per share)			$ 0.01
Rights Offering [Member] \| Board of Directors Chairman [Member]
Investment Owned, Percent of Net Assets			56.00%
Rights Offering [Member] \| Robert W. Duggan [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)			$ 0.001
Shares Issued, Price Per Share (in dollars per share)			$ 2.05
Equity Offering, Units, Sale of Units (in shares)			7,317,072
Number of Shares Per Unit Issued (in shares)			1
Number of Warrants Per Unit (in shares)			1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)			1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)			$ 2.05
Investment Owned, Percent of Net Assets			56.00%

Note 10 - Segment Reporting (Details Textual)	12 Months Ended
Note 10 - Segment Reporting (Details Textual)	Dec. 31, 2023
Number of Reportable Segments	1

Note 8 - Controlled Launch (Details Textual) $ in Thousands	12 Months Ended
Note 8 - Controlled Launch (Details Textual) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Feb. 28, 2021
Number of KOLs			70
Controlled Launch, Program Expenses	$ 0	$ 600
Revenue from Contract with Customer, Excluding Assessed Tax	0	700
CellFX System [Member]
Contract with Customer, Receivable, Credit Loss Expense (Reversal)		(500)
Controlled Launch [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		100
Redemption of Non Cash Credits [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0	$ 400
Minimum [Member]
Number of Patients Participating in Procedure			40
Maximum [Member]
Number of Patients Participating in Procedure			50

Note 4 - Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Supplemental Balance Sheet Disclosures [Text Block]

4. Balance Sheet Components

Property and Equipment, net

Property and equipment, net consisted of the following (in thousands):

	*December 31,*
	*2023*			*2022*
Leasehold improvements	$	2,519		$	2,519
Laboratory equipment		1,247			1,118
Furniture, fixtures and equipment		966			966
Software		272			289
Construction in progress		—			22
		5,004			4,914
Less: Accumulated depreciation and amortization		(3,476	)		(2,953	)
	$	1,528		$	1,961

Depreciation expense for the years ended December 31, 2023 and 2022, was $0.5 million and $0.7 million, respectively.

Intangible Assets, net

Intangible assets primarily consist of a license to utilize certain patents, know-how and technology relating to the Company’s NPS for biomedical applications acquired from Old Dominion University Research Foundation (ODURF), Eastern Virginia Medical School (EVMS), and the University of Southern California. In addition, the Company entered into a sponsored research agreement (“SRA”) with Old Dominion University’s Frank Reidy Research Center for Bioelectrics, a leading research organization in the field, which includes certain intellectual property rights arising from the research. The Company is amortizing the intangible assets over an estimated useful life of 12 years.

Intangible assets, net consisted of the following (in thousands):

	*December 31,*
	*2023*			*2022*
Acquired patents and licenses	$	7,985		$	7,985
Less: Accumulated amortization		(6,099	)		(5,434	)
	$	1,886		$	2,551

A schedule of the amortization of intangible assets is as follows (in thousands):

Years ending December 31:
2024	$	665
2025		665
2026		556
	$	1,886

Accrued Expenses

Accrued expenses consisted of the following (in thousands):

	*December 31,*
	*2023*		*2022*
Compensation expense	$	3,199	$	1,377
Director and officer liability insurance (Note 12)		—		571
Clinical trial fees and costs		84		64
Professional fees		343		318
Warranty		—		50
Other		188		215
	$	3,814	$	2,595

Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Finite-Lived Intangible Asset, Useful Life (Year)	12 years
Impairment, Long-Lived Asset, Held-for-Use, Total	$ 0
Goodwill, Impairment Loss	0
Liability for Uncertainty in Income Taxes, Noncurrent	$ 0	$ 0
Number of Operating Segments	1
Geographic Concentration Risk [Member] \| Assets, Total [Member] \| UNITED STATES
Concentration Risk, Percentage	100.00%	100.00%
General and Administrative Expense [Member]
Patent Costs	$ 500	$ 500
Minimum [Member] \| Equipment [Member]
Property, Plant and Equipment, Useful Life (Year)	3 years
Maximum [Member] \| Equipment [Member]
Property, Plant and Equipment, Useful Life (Year)	5 years

Note 10 - Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Disaggregation of Revenue [Table Text Block]

	Year Ended December 31,
	2023		2022
Systems	$	—	$	560
Cycle units		—		140
Total consolidated revenue	$	—	$	700

Revenue from External Customers by Geographic Areas [Table Text Block]

	Year Ended December 31,
	2023		2022
North America	$	—	$	517
Rest of World		—		183
Total consolidated revenue	$	—	$	700

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Stock Option Activity (Details) - The 2015 Plan, 2017 Plan and Inducement Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Options balances, number of shares (in shares)	5,250,696
Options balances, weighted average exercise price (in dollars per share)	$ 12.67
Options balances, weighted average remaining life (Year)	7 years 9 months 10 days	6 years 2 months 26 days
Options granted, number of shares (in shares)	5,338,386
Options granted, weighted average exercise price (in dollars per share)	$ 5.26
Options exercised, number of shares (in shares)	(301,254)
Options exercised, weighted average exercise price (in dollars per share)	$ 3.89
Options canceled, number of shares (in shares)	(316,494)
Options canceled, weighted average exercise price (in dollars per share)	$ 5.42
Options expired, number of shares (in shares)	(505,298)
Options expired, weighted average exercise price (in dollars per share)	$ 12.71
Options balances, number of shares (in shares)	9,466,036	5,250,696
Options balances, weighted average exercise price (in dollars per share)	$ 9.01	$ 12.67
Options exercisable, number of shares (in shares)	3,833,663
Options exercisable, weighted average exercise price (in dollars per share)	$ 13.67
Options exercisable, weighted average remaining life (Year)	5 years 6 months 21 days

Note 13 - Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Information Related to Right-of-use Assets and Lease Liabilities [Table Text Block]

	*Year Ended December 31,*
Assets:	*2023*		*2022*
Operating right-of-use assets	$	7,256	$	8,062

	*Year Ended December 31,*
Liabilities:	*2023*		*2022*
Lease liability, current	$	1,058	$	896
Lease liability, less current portion		8,086		9,144
Total lease liabilities	$	9,144	$	10,040

	Year Ended December 31,
	2023		2022
Cash paid for operating lease liabilities	$	1,845	$	1,806

Year ending December 31:
2024	$	1,910
2025		1,977
2026		2,046
2027		2,117
2028		2,191
Thereafter		1,883
Total lease payments		12,124
Less imputed interest		(2,980	)
Total lease liabilities	$	9,144

Weighted-average remaining lease term			5.83
Weighted-average discount rate			10	%

Note 10 - Segment Reporting

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Segment Reporting Disclosure [Text Block]

10. Segment Reporting

The Company operates and manages the business as one reportable and operating segment. The Company’s Chief Executive Officer acts as the CODM of the Company. The CODM reviews the results of the Company on a consolidated basis. In prior year, when making certain operating decisions and assessing performance, the CODM has additionally reviewed the disaggregated revenue results by product and geography. All of the Company’s long-lived assets are based in the United States.

Revenue by product consisted of the following (in thousands):

	Year Ended December 31,
	2023		2022
Systems	$	—	$	560
Cycle units		—		140
Total consolidated revenue	$	—	$	700

Revenue by geography consisted of the following (in thousands):

	Year Ended December 31,
	2023		2022
North America	$	—	$	517
Rest of World		—		183
Total consolidated revenue	$	—	$	700

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Note 10 - Segment Reporting - Revenue by Geography (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total revenues	$ 0	$ 700
North America [Member]
Total revenues	0	517
Rest of World [Member]
Total revenues	$ 0	$ 183

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 924
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-Name Accounting Standards Codification
-Section S99
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+ Details

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Rights Offering [Member] Common Stock [Member]	Rights Offering [Member] Additional Paid-in Capital [Member]	Rights Offering [Member] AOCI Attributable to Parent [Member]	Rights Offering [Member] Retained Earnings [Member]	Rights Offering [Member]	Private Placement [Member] Common Stock [Member]	Private Placement [Member] Additional Paid-in Capital [Member]	Private Placement [Member] AOCI Attributable to Parent [Member]	Private Placement [Member] Retained Earnings [Member]	Private Placement [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2021											29,716
Balance at Dec. 31, 2021											$ 29	$ 271,861	$ 0	$ (236,200)	$ 35,690
Issuance of shares (in shares)	7,317
Issuance of shares	$ 7	$ 14,857	$ 0	$ 0	$ 14,864
Issuance of shares under employee stock purchase plan (in shares)											188
Issuance of shares under employee stock purchase plan											$ 1	485	0	0	486
Issuance of shares upon exercise of warrants (in shares)											14
Issuance of shares upon exercise of warrants											$ 0	26	0	0	26
Stock-based compensation expense											0	5,191	0	0	5,191
Net loss											$ 0	0	0	(58,505)	(58,505)
Balance (in shares) at Dec. 31, 2022											37,235
Balance at Dec. 31, 2022											$ 37	292,420	0	(294,705)	(2,248)
Issuance of shares under employee stock purchase plan (in shares)											347
Issuance of shares under employee stock purchase plan											$ 1	394	0	0	395
Issuance of shares upon exercise of warrants (in shares)											7,238
Issuance of shares upon exercise of warrants											$ 7	14,821	0	0	14,828
Stock-based compensation expense											0	7,181	0	0	7,181
Net loss											$ 0	0	0	(42,210)	(42,210)
Issuance of common stock as part of debt extinguishment (in shares)						10,023
Issuance of common stock as part of debt extinguishment						$ 10	$ 65,233	$ 0	$ 0	$ 65,243
Issuance of common stock upon exercise of stock options (in shares)											301
Issuance of common stock upon exercise of stock options											$ 0	1,171	0	0	1,171
Balance (in shares) at Dec. 31, 2023											55,144
Balance at Dec. 31, 2023											$ 55	$ 381,220	$ 0	$ (336,915)	$ 44,360

Note 10 - Segment Reporting - Revenue by Product (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Total revenues	$ 0	$ 700
System Products [Member]
Total revenues	0	560
Cycle Units Products [Member]
Total revenues	$ 0	$ 140

- Definition

+ References

+ Details

Note 4 - Balance Sheet Components - Schedule of Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
2024	$ 665
2025	665
2026	556
Finite-Lived Intangible Assets, Net	$ 1,886	$ 2,551

Note 6 - Stockholders' Equity and Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

						*Weighted*
						*Average*
				*Weighted*		*Remaining*
	*Number of*			*Average*		*Contractual*
	*Shares*			*Exercise Price*		*Life (in Years)*
Warrants outstanding at December 31, 2022		7,303,832		$	2.05		4.43
Issued		—			—
Exercised		(7,237,657	)		2.05
Expired/Redeemed		(66,175	)		2.05
Warrants outstanding at December 31, 2023		—		$	—		—

Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Year Ended December 31,
	2023		2022
Cost of revenues	$	—	$	217
Research and development		3,491		1,563
Sales and marketing		—		733
General and administrative		3,690		2,678
Total stock-based compensation expense	$	7,181	$	5,191

Share-Based Payment Arrangement, Cost by Plan [Table Text Block]

	Year Ended December 31,
	2023		2022
Time-based options	$	3,827	$	4,467
Performance-based options		1,977		233
Market-based options		1,130		—
ESPP		247		491
Total stock-based compensation expense	$	7,181	$	5,191

Share-Based Payment Arrangement, Option [Member]

Notes Tables

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	*Year Ended December 31,*
	*2023*		*2022*
Expected term in years		5.0 - 8.0		5.3 - 6.8
Expected volatility		89 - 95%		83 - 88%
Risk-free interest rate		3.7 - 4.4%		1.9 - 3.2%
Dividend yield		—		—

	Year Ended December 31,
	2023		2022
Expected term in years		4.0 - 6.3		—
Expected volatility		90%		—
Risk-free interest rate		3.4% - 3.8%		—
Dividend yield		—		—

Market-based Options [Member]

Notes Tables

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	Stock Options Outstanding
	Number of shares		Weighted average exercise price		Weighted average remaining life (in years)
Balances — December 31, 2022		—	$	—		—
Options granted		2,100,000		6.78
Options exercised		—		—
Options canceled		—		—
Options expired		—		—
Balances — December 31, 2023		2,100,000	$	6.78		9.44
Exercisable — December 31, 2023		—		—		—

Performance Options [Member]

Notes Tables

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2022		520,302		$	10.08		7.02
Options granted		848,000			3.13
Options exercised		—			—
Options canceled		(53,500	)		2.31
Options expired		(90,672	)		11.35
Balances — December 31, 2023		1,224,130		$	5.51		8.53
Exercisable — December 31, 2023		443,628		$	7.57		7.75

Time-based Options [Member]

Notes Tables

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2022		4,730,394		$	12.95		6.16
Options granted		2,390,386			4.7
Options exercised		(301,254	)		3.89
Options canceled		(262,994	)		6.06
Options expired		(414,626	)		13.01
Balances — December 31, 2023		6,141,906		$	10.48		7.07
Exercisable — December 31, 2023		3,390,035		$	14.47		5.28

The 2017 Employee Stock Purchase Plan [Member]

Notes Tables

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year Ended December 31,
	2023		2022
Expected term in years		0.5 - 1.0		0.5 - 1.0
Expected volatility		83%		83%
Risk-free interest rate		5.1% - 5.5%		0.6% - 3.5%
Dividend yield		—		—

The 2015 Plan, 2017 Plan and Inducement Plan [Member]

Notes Tables

Share-Based Payment Arrangement, Option, Activity [Table Text Block]

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2022		5,250,696		$	12.67		6.24
Options granted		5,338,386			5.26
Options exercised		(301,254	)		3.89
Options canceled		(316,494	)		5.42
Options expired		(505,298	)		12.71
Balances — December 31, 2023		9,466,036		$	9.01		7.78
Exercisable — December 31, 2023		3,833,663		$	13.67		5.56

Note 3 - Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

		*December 31, 2023*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	41,184	$	—	$	—	$	41,184
Total assets measured at fair value		$	41,184	$	—	$	—	$	41,184

		*December 31, 2022*
Assets	*Classification*	*Level 1*		*Level 2*		*Level 3*		*Total*
Money market funds	Cash and cash equivalents	$	57,973	$	—	$	—	$	57,973
Total assets measured at fair value		$	57,973	$	—	$	—	$	57,973

Note 1 - Description of the Business

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]

1. Description of the Business

Pulse Biosciences, Inc. is a novel bioelectric medicine company committed to health innovation using its patented Nano-pulse Stimulation (“NPS”) technology, a revolutionary energy modality that delivers nanosecond-duration pulses of electrical energy, each less than a millionth of a second long, to non-thermally clear targeted cells while sparing adjacent noncellular tissue. NPS technology, also referred to as a Nanosecond Pulsed-Field Ablation (“nsPFA”) technology when used to ablate cellular tissue, can be used to treat a variety of medical conditions for which an optimal solution remains unfulfilled. The Company developed its proprietary CellFX System, a novel nsPFA delivery platform, and commercialized the initial application of its nsPFA technology to treat benign lesions of the skin. In parallel, the Company has designed a variety of applicators to explore the potential use of the CellFX platform to treat disorders in other medical specialties, such as cardiology, gastroenterology, gynecology, and ear nose and throat. These applicators include devices for open surgical procedures, endoscopic or minimally invasive procedures, and endoluminal catheters, and each has been used in preclinical studies. Based on our preclinical experience and the potential to significantly improve outcomes for patients in a large and growing market, the Company decided in 2022 to focus its efforts on the use of nsPFA and the CellFX platform in the treatment of atrial fibrillation (“AF”)

The Company was incorporated in Nevada on May 19, 2014. On June 18, 2018, the Company reincorporated from the State of Nevada to the State of Delaware. The Company is located in Hayward, California.

The Company’s activities are subject to significant risks and uncertainties, including the need for additional capital. The Company does not currently have any material cash flows from operations. It has minimal revenue and will need to raise additional capital to finance its operations. However, there can be no assurances that the Company will be able to obtain additional financing on acceptable terms and in the amounts necessary to fully fund its operating requirements.

Note 11 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Unrecognized Tax Benefits	$ 10,170	$ 8,925	$ 5,140
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	8,100	$ 10,800
Domestic Tax Authority [Member]
Operating Loss Carryforwards	222,000
Operating Loss Carryforwards, Not Subject to Expiration	196,400
Tax Credit Carryforward, Amount	8,600
State and Local Jurisdiction [Member]
Operating Loss Carryforwards	204,400
Tax Credit Carryforward, Amount	$ 8,100

Note 4 - Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Property, Plant and Equipment [Table Text Block]

	*December 31,*
	*2023*			*2022*
Leasehold improvements	$	2,519		$	2,519
Laboratory equipment		1,247			1,118
Furniture, fixtures and equipment		966			966
Software		272			289
Construction in progress		—			22
		5,004			4,914
Less: Accumulated depreciation and amortization		(3,476	)		(2,953	)
	$	1,528		$	1,961

Schedule of Finite-Lived Intangible Assets [Table Text Block]

	*December 31,*
	*2023*			*2022*
Acquired patents and licenses	$	7,985		$	7,985
Less: Accumulated amortization		(6,099	)		(5,434	)
	$	1,886		$	2,551

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]

Years ending December 31:
2024	$	665
2025		665
2026		556
	$	1,886

Schedule of Accrued Liabilities [Table Text Block]

	*December 31,*
	*2023*		*2022*
Compensation expense	$	3,199	$	1,377
Director and officer liability insurance (Note 12)		—		571
Clinical trial fees and costs		84		64
Professional fees		343		318
Warranty		—		50
Other		188		215
	$	3,814	$	2,595

Note 14 - Restructuring Charges

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Restructuring and Related Activities Disclosure [Text Block]

14. Restructuring Charges

On March 31, 2022, the Company initiated a plan to reduce its operating expenses, preserve financial resources, and focus its sales and marketing efforts on increasing utilization of CellFX Systems. The Company’s Board of Directors approved changes to the Company’s commercial leadership, restructuring of its commercial field organization and reductions in other personnel and expenses across the Company. The Company announced a reduction in force effective as of March 31, 2022. The affected employees were offered separation benefits, including severance payments along with temporary healthcare coverage assistance. The Company incurred a discrete restructuring related charge of $0.7 million which was fully recorded in March 2022 and the related expenses are included within total cost and expenses on the consolidated statement of operations for the year ended December 31, 2022. This charge represents the total amount to be incurred in connection with the activity. During the year ended December 31, 2022, the Company paid the entire $0.7 million.

On September 20, 2022, the Company initiated an additional reduction in force to align its workforce with its shift in strategic direction to advance its core NPS technology outside of dermatology. The reduction primarily impacted dermatological sales, marketing and other related support personnel. The affected employees were offered separation benefits, including severance payments along with temporary healthcare coverage assistance. The Company incurred a discrete restructuring related charge of $0.2 million which was fully recorded in September 2022 and the related expenses are included within total cost and expenses on the consolidated statement of operations for the year ended December 31, 2022. During the year ended December 31, 2022, the Company paid the entire $0.2 million.

In February 2023, the Company eliminated an additional seven positions and incurred a discrete restructuring related charge of $0.1 million which was fully recorded in February 2023 and the related expenses are included within total cost and expenses on the consolidated statement of operations for the year ended December 31, 2023. This charge represents the total amount incurred in connection with the activity.

Note 13 - Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Commitments and Contingencies Disclosure [Text Block]

13. Commitments and Contingencies

2022 Loan Agreement

On September 20, 2022, the Company and Robert W. Duggan, the Company's majority stockholder and Executive Chairman, entered into a Loan Agreement (“2022 Loan Agreement”) in connection with Mr. Duggan lending the principal sum of $65.0 million to the Company. The 2022 Loan Agreement bore interest at a rate per annum equal to 5.0%, payable quarterly commencing on January 1, 2023, with the principal sum payable on March 20, 2024. On March 17, 2023, the Company and Mr. Duggan amended certain terms of the 2022 Loan Agreement. There were no changes to the interest rate, but the principal sum repayment date was changed to September 30, 2024. During the year ended December 31, 2023, the Company made cash payments of $1.7 million for accrued interest on the loan, and recorded an additional $1.1 million of interest expense in relation to the 2022 Loan Agreement. On April 30, 2023, the Company entered into a Securities Purchase Agreement with Mr. Duggan, pursuant to which the Company agreed to issue and sell to Mr. Duggan 10,022,937 shares of the Company’s common stock, par value $0.001 per share, in a Private Placement, at a price per share of $6.51. These shares were paid for through the cancellation of the amounts then owed by the Company under the 2022 Loan Agreement, the principal sum of $65.0 million and all accrued and unpaid interest outstanding, which totaled approximately $0.2 million as of April 30, 2023. The parties completed the Private Placement on May 9, 2023 and, upon closing and satisfaction of the outstanding debt, the 2022 Loan Agreement terminated, without early termination fees or penalties being owed by the Company. No additional amounts are owed to Mr. Duggan under the 2022 Loan Agreement.

Operating Leases

In January 2017, the Company entered into a five-year lease (the “Existing Lease”) for approximately 15,700 square feet for its corporate headquarters located in Hayward, California. The lease commenced during July 2017.

In May 2019, the Company entered into Lease Amendment 1 (the “Lease Amendment”) in relation to the Existing Lease and added the lease of new premises of approximately 13,300 square feet and 21,300 square feet, (“Expansion Premises 1” and “Expansion Premises 2,” respectively). Additionally, the term of the Existing Lease was extended to October 2029 to be coterminous with Expansion Premises 1 and Expansion Premises 2.

The Company evaluated the lease amendment under the provisions of ASC 842. It concluded that the Lease Amendment would be accounted for as a single contract with the Existing Lease because the additional lease payments due to the Lease Amendment was not commensurate with the right-of-use asset granted to the Company. Though the Lease Amendment was accounted for as a single contract, the Existing Premises, Expansion Premises 1 (occupied in November 2019) and Expansion Premises 2 (occupied in May 2020) are accounted for as separate lease components. Accordingly, the Company measured and allocated consideration to each lease component as of the modification date.

During the years ended December 31, 2023 and 2022, rent expense, including common area maintenance charges, was $2.3 million and $2.1 million, respectively.

Supplemental balance sheet information related to leases (in thousands):

	*Year Ended December 31,*
Assets:	*2023*		*2022*
Operating right-of-use assets	$	7,256	$	8,062

	*Year Ended December 31,*
Liabilities:	*2023*		*2022*
Lease liability, current	$	1,058	$	896
Lease liability, less current portion		8,086		9,144
Total lease liabilities	$	9,144	$	10,040

Total cash paid for operating lease liabilities (in thousands):

	Year Ended December 31,
	2023		2022
Cash paid for operating lease liabilities	$	1,845	$	1,806

Maturities of operating lease liabilities were as follows (in thousands):

Year ending December 31:
2024	$	1,910
2025		1,977
2026		2,046
2027		2,117
2028		2,191
Thereafter		1,883
Total lease payments		12,124
Less imputed interest		(2,980	)
Total lease liabilities	$	9,144

Weighted-average remaining lease term and discount rate, as of December 31, 2023, were as follows:

Weighted-average remaining lease term			5.83
Weighted-average discount rate			10	%

Legal Proceedings

From time to time, we may be involved in a variety of claims, lawsuits, investigations, and proceedings relating to securities laws, product liability, patent infringement, contract disputes, and other matters relating to various claims that arise in the normal course of our business, including the matter described below. The outcome of any legal proceedings is unpredictable but, regardless of outcome, they can have an adverse impact on us because of defense and settlement costs, diversion of management resources, negative publicity, reputational harm, and other factors. We maintain insurance that may provide coverage for such matters, including customary employment practices liability insurance.

In November 2022, the employment of our former Chief Financial Officer, Sandra Gardiner, terminated. Ms. Gardiner’s departure was not the result of any disagreement with the Company on any matter relating to its operations, accounting policies or practices, although the Company determined that she was not eligible to receive any severance benefits under the terms and conditions of her then existing employment agreement. In March 2023, Ms. Gardiner filed an arbitration demand with JAMS seeking severance benefits and other remedies, alleging breach of contract and unlawful termination in violation of public policy, among other things. We believe that Ms. Gardiner’s claims are without merit and we intend to vigorously defend ourselves against them. Because of the difficulty in predicting the outcome of any legal proceeding, particularly one that is in its early stages, the Company is not able to conclude that a liability is probable and cannot predict what the final outcome of Ms. Gardiner’s arbitration proceeding will likely be or provide a reasonable estimate for the range of ultimate possible loss, if any. However, at this time, we believe that the final resolution of this matter will not adversely affect our consolidated position, results of operations, or cash flows and that a liability is not probable at this time.

Note 17 - Subsequent Events (Details Textual) - The 2017 Inducement Equity Incentive Plan [Member] - shares	1 Months Ended
	Mar. 31, 2024	May 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)		1,000,000
Subsequent Event [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)	2,000,000

Note 14 - Restructuring Charges (Details Textual) - Employee Severance [Member] $ in Millions	1 Months Ended
	Feb. 28, 2023 USD ($)	Sep. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)
Restructuring and Related Cost, Number of Positions Eliminated	7
March 2022 Restructuring Plan [Member]
Payments for Restructuring			$ 0.7
September 2022 Restructuring Plan [Member]
Payments for Restructuring		$ 0.2
Total Cost and Expenses [Member]
Restructuring Charges, Total	$ 0.1
Total Cost and Expenses [Member] \| March 2022 Restructuring Plan [Member]
Restructuring Charges, Total			$ 0.7
Total Cost and Expenses [Member] \| September 2022 Restructuring Plan [Member]
Restructuring Charges, Total		$ 0.2

Note 13 - Commitments and Contingencies (Details Textual) $ / shares in Units, $ in Millions		12 Months Ended
	Apr. 30, 2023 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2022 USD ($) $ / shares	Sep. 20, 2022 USD ($)	May 31, 2019 a	Jul. 31, 2017 a
Common Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares		$ 0.001	$ 0.001
Operating Lease, Expense		$ 2.3	$ 2.1
Corporate Headquarters in Hayward, California [Member]
Lessee, Operating Lease, Term of Contract (Year)						5 years
Area of Real Estate Property (Acre) \| a						15,700
Corporate Headquarters in Hayward, California [Member] \| Expansion Premises 1 [Member]
Area of Real Estate Property (Acre) \| a					13,300
Corporate Headquarters in Hayward, California [Member] \| Expansion Premises 2 [Member]
Area of Real Estate Property (Acre) \| a					21,300
Robert W. Duggan [Member] \| Private Placement [Member]
Stock Issued During Period, Shares, New Issues (in shares) \| shares	10,022,937
Common Stock, Par or Stated Value Per Share (in dollars per share) \| $ / shares	$ 0.001
Shares Issued, Price Per Share (in dollars per share) \| $ / shares	$ 6.51
Two Thousand Twenty Two Loan Agreement [Member] \| Robert W. Duggan [Member]
Debt Instrument, Face Amount				$ 65.0
Debt Instrument Quarterly Interest Rate				5
Debt Instrument, Increase, Accrued Interest		1.7
Interest Expense		$ 1.1
Loan Agreement [Member]
Debt Instrument, Decrease, Forgiveness	$ 65.0
Interest Payable	$ 0.2

Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2023	Mar. 20, 2024	Jun. 30, 2023
Document Information [Line Items]
Entity Central Index Key	0001625101
Entity Registrant Name	Pulse Biosciences, Inc.
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-34899
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5696597
Entity Address, Address Line One	3957 Point Eden Way
Entity Address, City or Town	Hayward
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94545
City Area Code	510
Local Phone Number	906-4600
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	PLSE
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 124,067,534
Entity Common Stock, Shares Outstanding		55,225,333
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	San Francisco, California

Note 4 - Balance Sheet Components (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Depreciation	$ 542	$ 690
Finite-Lived Intangible Asset, Useful Life (Year)	12 years

Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	55,144,000	37,235,000
Common stock, shares outstanding (in shares)	55,144,000	37,235,000

Note 5 - Goodwill (Details Textual) $ in Thousands	12 Months Ended
Note 5 - Goodwill (Details Textual) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2022 USD ($)
Goodwill, Ending Balance	$ 2,791		$ 2,791
Goodwill, Impairment Loss	$ 0
Series of Individually Immaterial Business Acquisitions [Member]
Number of Businesses Acquired		3
Business Combination, Consideration Transferred, Total		$ 5,500
Goodwill, Ending Balance		$ 2,800

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References + Details

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenues:
Total revenues	$ 0	$ 700
Cost and expenses:
Cost of revenues	0	11,944
Research and development	27,797	20,839
Sales and marketing	0	12,019
General and administrative	15,777	13,955
Total cost and expenses	43,574	58,757
Loss from operations	(43,574)	(58,057)
Other income (expense):
Interest income (expense), net	1,364	(448)
Total other income (expense)	1,364	(448)
Loss from operations, before income taxes	(42,210)	(58,505)
Income tax benefit	0	0
Net loss	(42,210)	(58,505)
Comprehensive loss	$ (42,210)	$ (58,505)
Net loss per share:
Basic and diluted net loss per share (in dollars per share)	$ (0.88)	$ (1.72)
Weighted average shares used to compute net loss per common share — basic and diluted (in shares)	48,038	33,935

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Market-based Option Activity (Details) - Market-based Options [Member]	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Options balances, number of shares (in shares) \| shares	0
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options granted, number of shares (in shares) \| shares	2,100,000
Options granted, weighted average exercise price (in dollars per share) \| $ / shares	$ 6.78
Options exercised, number of shares (in shares) \| shares	0
Options exercised, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options canceled, number of shares (in shares) \| shares	0
Options canceled, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options expired, number of shares (in shares) \| shares	0
Options expired, weighted average exercise price (in dollars per share) \| $ / shares	$ 0
Options balances, number of shares (in shares) \| shares	2,100,000
Options balances, weighted average exercise price (in dollars per share) \| $ / shares	$ 6.78
Options balances, weighted average remaining life (Year)	9 years 5 months 8 days
Options exercisable, number of shares (in shares) \| shares	0
Options exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 0

Note 15 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	$ 0

Note 5 - Goodwill

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Goodwill Disclosure [Text Block]

5. Goodwill

In 2014, the Company acquired three companies (the acquisitions) for aggregate consideration of $5.5 million. In accordance with ASC Topic 805, Business Combinations, the Company recorded goodwill of $2.8 million in connection with the acquisitions, which represents the excess of consideration paid over the fair value of net tangible and intangible assets acquired.

The Company reviews goodwill for impairment annually or whenever changes in circumstances indicate that the carrying amount of goodwill may not be recoverable. Based on the Company’s annual review as of December 31, 2023, the Company determined that its goodwill was not impaired.

Note 6 - Stockholders' Equity and Stock-based Compensation - ESPP Assumptions (Details) - The 2017 Employee Stock Purchase Plan [Member]	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Expected volatility	83.00%	83.00%
Dividend yield	0.00%	0.00%
Minimum [Member]
Expected term in years (Year)	6 months	6 months
Risk-free interest rate	5.10%	0.60%
Maximum [Member]
Expected term in years (Year)	1 year	1 year
Risk-free interest rate	5.50%	3.50%

Note 11 - Income Taxes - Reconciliation of Unrecognized Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Unrecognized tax benefits at beginning of year	$ 8,925	$ 5,140
Increases related to current year tax positions	1,575	2,055
Increases related to prior year tax positions	1,129	1,730
Decreases related to prior year tax positions	(1,459)	0
Unrecognized tax benefits at beginning of year	$ 10,170	$ 8,925

Note 9 - Revenue

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Revenue from Contract with Customer [Text Block]

9. Revenue

In connection with its Controlled Launch program in dermatology, the Company recognized revenue at a point in time when it satisfied performance obligations by transferring control of promised goods to its customers. The amount of revenue recognized was equal to the consideration which the Company was entitled to in exchange for the promised goods, excluding any amounts assessed by government authorities for taxes which might be collected from a customer. This consideration may include non-cash services performed, as was the case with revenue recognized in connection with the Controlled Launch program. On September 20, 2022, the Company announced its shift in focus to advance its core NPS technology outside of dermatology and concluded its Controlled Launch program. The Company has not recognized any revenue during the year ended December 31, 2023. Total revenue recognized for the year ended December 31, 2022, was $0.7 million of which approximately $0.4 million was driven by the redemption of non-cash credits earned as part of the Controlled Launch, with the balances driven by cash purchases of cycle units (“CUs”) and CellFX commercial consoles sold.

Dermatology sales contracts often involved the sale and delivery of multiple performance obligations in the contract.

Performance Obligations

In the Controlled Launch, systems consisted of the CellFX console and its embedded software, handpieces, and disposable tips. The console was a physical piece of hardware used by the dermatology customer to perform patient procedures. Individually the console and software were not distinct, therefore the Company combined the console and embedded software to form one distinct system performance obligation. Payment for systems was generally due prior to shipment, and the system performance obligation was satisfied upon shipment of the system to the customer.

Handpieces were attached to the console and used in conjunction with tips to perform patient procedures. Generally, in the Controlled Launch, upon initial sale of a system to a customer, the Company included two handpieces. The handpiece had a shorter expected useful life than the console, and a customer could purchase additional handpieces when needed, as they were available for sale on a stand-alone basis. Payment for handpieces was generally due prior to shipment, and handpieces represented a distinct performance obligation which was satisfied either upon shipment, or upon delivery of the handpiece to the customer, depending on the specific contract.

Tips are single-patient multiple-use products that come in different sizes, each of which are to be used for specific procedures. Tips are attached to the handpiece for use in patient procedures and, upon detachment from the handpiece, a tip cannot be reused, and it must be disposed of. Tips represent a distinct performance obligation which is satisfied either upon shipment, or upon delivery of the tips to the customer, depending on the specific contract.

CUs, which are also still available for existing customers, are credits that authorize the customer to perform a procedure, or cycle. Each procedure requires a specific number of CUs, dependent upon type of tip used and procedure level selected. As the procedure is performed, the applicable number of CUs are decremented. During part of the Controlled Launch, customers purchased CUs; when the customer’s balance of CUs on a specific system was depleted, the system would no longer function until the customer purchased additional CUs. At that time, customers could purchase additional CUs via the Company’s CellFX Marketplace which was an online marketplace accessible directly from the CellFX System. Payment for CUs was due upon order placement and the CUs were immediately available for download to the console via CellFX CloudConnect. At that time, CUs represented a distinct performance obligation which was satisfied when CUs were made available for customers to download from the Company’s CellFX CloudConnect, as customers could use purchased CUs at any time at their discretion, and the Company did not provide any ongoing service or other forms of involvement after the sale occurred.

Shipping and handling activities are not considered to be a separate performance obligation. The Company’s standard commercial agreements generally include FOB shipping point terms. The Company has made an accounting policy election to account for shipping and handling costs as fulfillment costs because the shipping and handling activities occur after the customer obtains control of the product.

Transaction Price

In the Controlled Launch, the transaction price was the consideration to which the Company expected to be entitled to in exchange for providing the promised goods to customers. Customer orders placed for cash contemplated a fixed amount of consideration. Customer orders placed by physicians participating in the Controlled Launch when they elected to purchase the CellFX System were paid for via conversion of accumulated earned credits for prior services provided by the physicians under the terms of their participation in the Controlled Launch. For these transactions, the transaction price included noncash consideration. The services rendered by the physicians in the Controlled Launch were accounted for separately from the subsequent sales of the CellFX Systems because they were distinct from the system sales. They were distinct because they provided the Company with treatment data that could also be procured, and historically had been procured by the Company, without the corresponding system sales. This data was used by the Company to enhance marketing and promotion of its products.

The Company evaluated the possible impact of variable consideration in determining the transaction price, in particular the possibility of future returns or credits. Still outstanding sales agreements allow for a right of return only if the product does not conform to the agreed upon quality standards or if the product was shipped due to Company error. The Company anticipates such returns will be minimal and has made no adjustments to the transaction price for any estimated returns. The transaction price is determined at the time of the initial revenue recognition and updated each quarter for any changes in circumstances (e.g., changes in estimated return or credit rates).

The Company has made an accounting policy election to exclude from the measurement of the transaction price all taxes which are imposed on and concurrent with a specific revenue-producing transaction and collected by the entity from a customer.

When there are multiple performance obligations present, the total transaction price shall be allocated to each of the performance obligations based upon the relative SSPs of those performance obligations. The Company establishes SSPs based on multiple factors including, prices charged by the Company for similar offerings, product-specific business objectives, and the estimated cost to provide the performance obligation. However, upon the sale of a new CellFX System, all performance obligations are delivered concurrently and therefore there is no impact to revenue recognition timing, and the Company has determined allocations are not necessary. Should the customer purchase additional CUs, handpieces, or tips at a later time, those purchases will be made under separate purchase agreements, with all promised goods generally transferred at the same time, therefore no price allocation is necessary in that scenario either.

Controlled Launch Agreements

In August 2021, the Company began to recognize revenue in relation to the conversion of Controlled Launch Program participants into sales agreements (Note 8). These customers were already in possession of the system, handpiece, and tips. As such, upon execution of these purchase agreements, the Company recognized revenue on the agreements because control of all performance obligations were transferred at that time. These customers separately purchased CUs in order to operate the CellFX System and the revenue for these CUs was recognized upon delivery of the CUs to CellFX CloudConnect.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-9

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org//606/tableOfContent

+ Details

Note 9 - Revenue (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Note 9 - Revenue (Details Textual) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0	$ 700
Redemption of Non Cash Credits [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0	$ 400

- Definition

+ References

+ Details

Note 11 - Income Taxes - Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Domestic	$ (42,210)	$ (58,505)
Foreign	0	0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ (42,210)	$ (58,505)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(11))
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Consolidation, Policy [Policy Text Block]

Principles of Consolidation

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

Concentration Risk, Credit Risk, Policy [Policy Text Block]

Concentration of Credit Risk

Fair Value of Financial Instruments, Policy [Policy Text Block]

Fair Value of Financial Instruments

Cash and Cash Equivalents, Policy [Policy Text Block]

Cash and Cash Equivalents

The Company invests its cash primarily in money market funds. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.

Property, Plant and Equipment, Policy [Policy Text Block]

Property and Equipment

Inventory, Policy [Policy Text Block]

Valuation of Inventory

Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block]

Intangible Assets

The Company’s intangible assets consist of acquired patents and licenses, which are amortized over their estimated useful lives of twelve years.

Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]

Long-Lived Assets

Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]

Goodwill

Revenue from Contract with Customer [Policy Text Block]

Revenue from Contracts with Customers

Standard Product Warranty, Policy [Policy Text Block]

Product Warranty

Warranty accrual activity consisted of the following (in thousands):

	*Year Ended December 31,*
	*2023*			*2022*
Beginning balance	$	50		$	80
Add: Accruals for warranties issued during the period		—			42
Less: Adjustment for inventory at cost and excessive and obsolete inventory		(50	)		(72	)
Ending balance	$	—		$	50

Share-Based Payment Arrangement [Policy Text Block]

Stock-Based Compensation

The Company's stock-based compensation programs include stock options and an employee stock purchase program.

See Note 6 for a detailed discussion of the Company’s stock plans and stock-based compensation expense.

Research and Development Expense, Policy [Policy Text Block]

Research and Development Costs

Patent Costs [Policy Text Block]

Patent Costs

Income Tax, Policy [Policy Text Block]

Income Taxes

Comprehensive Income, Policy [Policy Text Block]

Comprehensive Loss

Earnings Per Share, Policy [Policy Text Block]

Net Loss per Share

	Year Ended December 31,
	2023		2022
Common stock warrants		—		7,303,832
Common stock options		9,466,036		5,250,696
Total		9,466,036		12,554,528

Segment Reporting, Policy [Policy Text Block]

Segment and Geographical Information

See Note 10 for details of revenue by product and geography.

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Accounting Pronouncements Not Yet Adopted

Note 3 - Fair Value of Financial Instruments (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Impairment of Marketable Securities	$ 0	$ 0
Fair Value, Level 1, 2 and 3 Transfers, Amount	0	0
Assets, Fair Value Disclosure	41,184	57,973
Fair Value, Recurring [Member]
Liabilities, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	$ 0	$ 0

Note 6 - Stockholders' Equity and Stock-based Compensation

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Share-Based Payment Arrangement [Text Block]

6. Stockholders’ Equity and Stock-Based Compensation

Preferred Stock

The Company has authorized a total of 50,000,000 shares of preferred stock, par value $0.001 per share, none of which were outstanding at December 31, 2023 and 2022. The Company’s Board of Directors (the “Board”) has the authority to issue preferred stock and to determine the rights, preferences, privileges, and restrictions, including voting rights, without any further vote or action by the Company’s stockholders.

Common Stock

The Company has authorized a total of 500,000,000 shares of common stock, par value $0.001 per share.

Private Placement Securities Purchase Agreement

On April 30, 2023, the Company entered into a Securities Purchase Agreement with Robert W. Duggan, the Company’s majority stockholder and Executive Chairman, pursuant to which the Company agreed to issue and sell to Mr. Duggan 10,022,937 shares of the Company’s common stock, par value $0.001 per share, in a Private Placement, at a price per share of $6.51. The parties completed the Private Placement on May 9, 2023, after satisfying all pre-closing conditions, and the Company issued the full number of shares to Mr. Duggan. The shares were paid for through the cancellation of the principal sum of $65.0 million borrowed by the Company pursuant to the 2022 Loan Agreement (See Note 13), together with all accrued and unpaid interest outstanding owed at the time of closing.

Rights Offering

On June 9, 2022, the Company completed a rights offering (the “2022 Rights Offering") resulting in the sale of 7,317,072 units (the “Units”), at a price of $2.05 per Unit, with each Unit consisting of one share of the Company’s common stock, par value $0.001 per share, and one warrant (the “2022 Rights Offering Warrants”) to purchase one share of common stock at a price of $2.05 per share. The common stock and warrants comprising the Units separated upon the closing of the 2022 Rights Offering and were issued individually. 7,317,072 shares of common stock and warrants to acquire up to an additional 7,317,072 shares of common stock were issued in the 2022 Rights Offering. The Company received aggregate gross proceeds from the 2022 Rights Offering of $15 million. In May 2023, the Company delivered an irrevocable notice of redemption to warrant holders and, on June 16, 2023, it redeemed the last of the outstanding 2022 Rights Offering Warrants at a price of $0.01 per warrant share. See the Common Stock Warrants section below for further details. Robert W. Duggan, the Company’s majority stockholder and Executive Chairman, purchased approximately 56% of the shares offered through the 2022 Rights Offering.

Common Stock Warrants

In connection with the 2022 Rights Offering, the Company issued 2022 Rights Offering Warrants to purchase a total of 7,317,072 shares of its common stock at an exercise price of $2.05. The 2022 Rights Offering Warrants were subject to redemption by the Company for $0.01 per underlying share of common stock, on not less than 30 days written notice, if the volume weighted average price of the Company’s common stock equals or exceeds 200% of the exercise price for the warrants, subject to adjustment, per share, for 20 consecutive trading days, provided that the Company may not redeem the warrants prior to the date that is three months after the issuance date. On May 10, 2023, the Company issued a press release announcing that on May 9, 2023 the terms for warrant redemption had been met. Pursuant to the redemption, the Company redeemed 66,175 warrants on the redemption date, June 16, 2023. Prior to the redemption date, warrants to purchase 7,250,897 shares were exercised, generating approximately $14.9 million of total gross proceeds to the Company. As of December 31, 2023, there were no 2022 Rights Offering Warrants outstanding.

A summary of total warrants activity for the year ended December 31, 2023 is presented below:

						*Weighted*
						*Average*
				*Weighted*		*Remaining*
	*Number of*			*Average*		*Contractual*
	*Shares*			*Exercise Price*		*Life (in Years)*
Warrants outstanding at December 31, 2022		7,303,832		$	2.05		4.43
Issued		—			—
Exercised		(7,237,657	)		2.05
Expired/Redeemed		(66,175	)		2.05
Warrants outstanding at December 31, 2023		—		$	—		—

Equity Plans

2017 Equity Incentive Plan and 2017 Inducement Equity Incentive Plan

The Board of Directors of the Company (the "Board") previously adopted, and the Company’s stockholders approved, the Company’s 2017 Equity Incentive Plan (the “2017 Plan”).

The 2017 Plan has a 10-year term, and provides for the grant of stock options, stock appreciation rights, restricted stock, RSUs, performance units, and performance shares to employees, directors and consultants of the Company and any parent or subsidiary of the Company, as the Compensation Committee of the Board may determine. Subject to an annual evergreen increase and adjustment in the case of certain capitalization events, the Company initially reserved 1,500,000 shares of the Company’s common stock for issuance pursuant to awards under the 2017 Plan. In addition, shares remaining available under the Company’s 2015 Equity Incentive Plan, as amended (the “2015 Plan”), and shares reserved but not issued pursuant to outstanding equity awards that expire or terminate without being exercised or that are forfeited or repurchased by the Company will be added to the shares of common stock available for issuance under the 2017 Plan. The 2017 Plan is administered by the Board’s Compensation Committee. Effective January 1, 2023 and 2022, the number of shares of common stock available under the 2017 Plan increased by 1,200,000 and 1,188,657 shares, respectively, pursuant to the evergreen provision of the 2017 Plan. Under the evergreen provision of the 2017 Plan, the share increase is determined based on the least of (i) 1,200,000 shares, (ii) 4% of the Company’s common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Board. Additionally, in December 2023, the number of shares of common stock available under the 2017 Plan increased by 1,375,000 shares as a result of a stockholder vote held at a special meeting of stockholders. As of December 31, 2023, 231,763 shares of common stock remained available for issuance under the 2017 Plan.

During November 2017, the Board of the Company adopted the 2017 Inducement Equity Incentive Plan (the “Inducement Plan”) and reserved 1,000,000 shares of the Company’s common stock for issuance pursuant to equity awards granted under the Inducement Plan. The Inducement Plan was adopted without stockholder approval.

The Inducement Plan has a 10-year term and provides for the grant of equity-based awards, including non-statutory stock options, RSUs, restricted stock, stock appreciation rights, performance shares and performance units, and its terms are substantially similar to the 2017 Plan, including with respect to treatment of equity awards in the event of a “merger” or “change in control” as defined under the Inducement Plan. Options issued under the Inducement Plan may have a term up to ten years and have variable vesting provisions. New hire grants generally vest 25% per year starting upon the first anniversary of the grant. Equity-based awards issued under the Inducement Plan are only issuable to individuals not previously engaged as employees or non-employee directors of the Company prior to the Inducement Plan’s adoption date. In May 2021, the Board approved an amendment to the Inducement Plan to reserve an additional 1,000,000 shares of the Company’s common stock for issuance pursuant to the Inducement Plan. And, in March 2024, the Board approved a second amendment to the Inducement Plan to reserve an additional 2,000,000 shares of the Company’s common stock for issuance pursuant to the Inducement Plan. As of December 31, 2023, 1,249,126 shares of common stock were available for issuance under the Inducement Plan.

A summary of stock option activity under the 2015 Plan, 2017 Plan and Inducement Plan for the year ended December 31, 2023 is presented below:

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2022		5,250,696		$	12.67		6.24
Options granted		5,338,386			5.26
Options exercised		(301,254	)		3.89
Options canceled		(316,494	)		5.42
Options expired		(505,298	)		12.71
Balances — December 31, 2023		9,466,036		$	9.01		7.78
Exercisable — December 31, 2023		3,833,663		$	13.67		5.56

Time-based Options

The Company awards time-based options which vest and become exercisable, subject to the individual’s continued employment or service through the applicable vesting date. Time-based options can have various vesting schedules, most commonly new hire grants which generally vest 25% per year starting upon the first anniversary of the grant.

A summary of the time-based stock option activity under the 2015 Plan, 2017 Plan and Inducement Plan for the year ended December 31, 2023 is presented below:

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2022		4,730,394		$	12.95		6.16
Options granted		2,390,386			4.7
Options exercised		(301,254	)		3.89
Options canceled		(262,994	)		6.06
Options expired		(414,626	)		13.01
Balances — December 31, 2023		6,141,906		$	10.48		7.07
Exercisable — December 31, 2023		3,390,035		$	14.47		5.28

The intrinsic value of time-based options exercised during the years ended December 31, 2023 and 2022 was $0.9 million and zero, respectively.

The fair value of the time-based options granted to employees and directors during the years ended December 31, 2023 and 2022 was $9.0 million and $2.3 million, respectively.

Performance Options

Certain stock options awarded to the Company’s executives and other employees contain performance conditions related to certain financial measures and achievements of strategic and operational milestones. The options will vest and become exercisable once the specific performance condition is fulfilled.

A summary of the performance option activity under the 2017 Plan and Inducement Plan for the year ended December 31, 2023 is presented below:

	*Stock Options Outstanding*
	*Number of shares*			*Weighted average exercise price*		*Weighted average remaining life (in years)*
Balances — December 31, 2022		520,302		$	10.08		7.02
Options granted		848,000			3.13
Options exercised		—			—
Options canceled		(53,500	)		2.31
Options expired		(90,672	)		11.35
Balances — December 31, 2023		1,224,130		$	5.51		8.53
Exercisable — December 31, 2023		443,628		$	7.57		7.75

The fair value of the performance options granted to employees during the years ended December 31, 2023 and 2022 was $2.0 million and $0.8 million, respectively.

Market-based Options

Certain stock options awarded by the Company contain market conditions related to achievement of certain market capitalization targets. The options will vest and become exercisable once the specific market capitalization target is fulfilled.

A summary of the market-based option activity under the 2017 Plan for the year ended December 31, 2023 is presented below:

	Stock Options Outstanding
	Number of shares		Weighted average exercise price		Weighted average remaining life (in years)
Balances — December 31, 2022		—	$	—		—
Options granted		2,100,000		6.78
Options exercised		—		—
Options canceled		—		—
Options expired		—		—
Balances — December 31, 2023		2,100,000	$	6.78		9.44
Exercisable — December 31, 2023		—		—		—

The fair value of the market-based options granted to employees during the year ended December 31, 2023 was $10.5 million. There were no market-based options granted during the year ended December 31, 2022.

The Company estimates the fair value of time-based and performance-based stock options on the grant date using the Black-Scholes option pricing model. The estimated fair value of these employee stock options is amortized on a straight-line basis over the requisite service period of the awards. The Company reviews, and when deemed appropriate, updates the assumptions used on a periodic basis. The fair value of time-based and performance-based stock options was estimated using the following weighted-average assumptions:

	*Year Ended December 31,*
	*2023*		*2022*
Expected term in years		5.0 - 8.0		5.3 - 6.8
Expected volatility		89 - 95%		83 - 88%
Risk-free interest rate		3.7 - 4.4%		1.9 - 3.2%
Dividend yield		—		—

The Company estimates the fair value of market-based stock options on the grant date using a Monte Carlo simulation model. The estimated fair value of these employee stock options is amortized over the requisite service period for each tranche of the awards. The requisite service period is the service period derived from the Monte Carlo simulation model. If the market capitalization targets are met sooner than the derived service period, the Company will accelerate the recognition of stock-based compensation expense to reflect the cumulative expense associated with the vested shares. The fair value of market-based stock options was estimated using the following weighted-average assumptions:

	Year Ended December 31,
	2023		2022
Expected term in years		4.0 - 6.3		—
Expected volatility		90%		—
Risk-free interest rate		3.4% - 3.8%		—
Dividend yield		—		—

2017 Employee Stock Purchase Plan

The Board previously adopted and the stockholders approved the Company’s 2017 Employee Stock Purchase Plan (the “2017 ESPP”).

The 2017 ESPP is a broad-based plan that provides employees of the Company and its designated affiliates with the opportunity to become stockholders through periodic payroll deductions that are applied towards the purchase of Company common shares at a discount from the then-current market price. Subject to adjustment in the case of certain capitalization events, a total of 250,000 common shares of the Company were available for purchase at adoption of the 2017 ESPP. Pursuant to the 2017 ESPP, the annual share increase pursuant to the evergreen provision is determined based on the least of (i) 450,000 shares, (ii) 1.5% of the Company’s common stock outstanding at December 31 of the immediately preceding year, or (iii) such number of shares as determined by the Board. The Board waived the evergreen provision for 2022 and 2023 and no additional shares were reserved under the 2017 ESPP. During the years ended December 31, 2023 and 2022, the Company issued 347,681 and 188,097 shares of common stock under the 2017 ESPP, respectively. As of December 31, 2023, 113,318 shares of common stock remained available for issuance under the 2017 ESPP.

The Company estimates the fair value of ESPP grants on their grant date using the Black-Scholes option pricing model. The estimated fair value of ESPP grants is amortized on a straight-line basis over the requisite service period of the grants. The Company reviews, and when deemed appropriate, updates the assumptions used on a periodic basis. The Company utilizes its estimated volatility in the Black-Scholes option pricing model to determine the fair value of ESPP grants. The fair value of ESPP grants was estimated using the following weighted-average assumptions:

	Year Ended December 31,
	2023		2022
Expected term in years		0.5 - 1.0		0.5 - 1.0
Expected volatility		83%		83%
Risk-free interest rate		5.1% - 5.5%		0.6% - 3.5%
Dividend yield		—		—

Stock-based Compensation

Total stock-based compensation expense recorded in the consolidated statements of operations and comprehensive loss was as follows (in thousands):

	Year Ended December 31,
	2023		2022
Cost of revenues	$	—	$	217
Research and development		3,491		1,563
Sales and marketing		—		733
General and administrative		3,690		2,678
Total stock-based compensation expense	$	7,181	$	5,191

As of December 31, 2023, not all of the performance conditions of the performance options are probable to be achieved. Compensation expense has only been recognized for those conditions that are assumed to be probable.

Total stock-based compensation expense by award type was as follows (in thousands):

	Year Ended December 31,
	2023		2022
Time-based options	$	3,827	$	4,467
Performance-based options		1,977		233
Market-based options		1,130		—
ESPP		247		491
Total stock-based compensation expense	$	7,181	$	5,191

At December 31, 2023, there was $9.7 million of unrecognized compensation cost related to unvested stock-based compensation arrangements, which is expected to be recognized over a weighted average period of 4.19 years.

Note 7 - Research Grants and Agreements

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Research, Development, and Computer Software Disclosure [Text Block]

7. Research Grants and Agreements

Sponsored Research Agreement

The Company entered into a SRA with ODURF during 2014 pursuant to which the Company sponsors research activities performed by ODURF’s Frank Reidy Center. ODURF is compensated by the Company for its conduct of each study in accordance with the budget and payment terms set forth in the applicable task order. In March 2021, the Company agreed to sponsor a task order for research in the amount of $0.3 million and in May 2021 sponsored an additional task order for $0.3 million each to be performed during their respective subsequent 12-month periods. These sponsored researches are funded through monthly payments made upon ODURF certifying, to the Company's reasonable satisfaction, that ODURF has met its obligations pursuant to the specified task order and statement of work. The principal investigator may transfer funds within the budget as needed with our approval so long as the obligations of ODURF under the task order and statement of work remain unchanged and unimpaired. During the years ended December 31, 2023 and 2022, the Company incurred costs relating to the SRA equal to zero and $0.2 million, respectively. As of December 31, 2023, there are no unbilled SRAs left under the task orders.

Note 15 - Employee Benefit Plans

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Retirement Benefits [Text Block]

15. Employee Benefit Plans

The Company sponsors a defined contribution plan under which it may make discretionary contributions. The Company did not make any employer matching contributions to this plan during the years ended December 31, 2023 and 2022.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480794/715-70-50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (q)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//715/tableOfContent

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (o)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (p)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (r)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (r)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480126/715-20-S99-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 60
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Note 6 - Stockholders' Equity and Stock-based Compensation - Summary of Performance Option Activity (Details) - Performance Options [Member] - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Options balances, number of shares (in shares)	520,302
Options balances, weighted average exercise price (in dollars per share)	$ 10.08
Options balances, weighted average remaining life (Year)	8 years 6 months 10 days	7 years 7 days
Options granted, number of shares (in shares)	848,000
Options granted, weighted average exercise price (in dollars per share)	$ 3.13
Options exercised, number of shares (in shares)	0
Options exercised, weighted average exercise price (in dollars per share)	$ 0
Options canceled, number of shares (in shares)	(53,500)
Options canceled, weighted average exercise price (in dollars per share)	$ 2.31
Options expired, number of shares (in shares)	(90,672)
Options expired, weighted average exercise price (in dollars per share)	$ 11.35
Options balances, number of shares (in shares)	1,224,130	520,302
Options balances, weighted average exercise price (in dollars per share)	$ 5.51	$ 10.08
Options exercisable, number of shares (in shares)	443,628
Options exercisable, weighted average exercise price (in dollars per share)	$ 7.57
Options exercisable, weighted average remaining life (Year)	7 years 9 months

Note 11 - Income Taxes - Deferred Tax Asset (Liability) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accruals	$ 1,502	$ 3,404
Net operating loss carryforwards	61,072	56,447
Tax credit carryforwards	9,815	7,111
Stock-based compensation	7,704	8,784
R&D capitalization	7,384	3,810
Lease liability	1,920	2,948
Fixed assets	(7)	0
Intangibles	(99)	0
Gross deferred tax assets	89,503	82,504
Valuation allowance	(87,853)	(79,779)
Total deferred tax assets	1,650	2,725
Intangibles	0	(117)
Right-of-use asset	(1,650)	(2,593)
Fixed assets	0	(15)
Total deferred tax liabilities	(1,650)	(2,725)
Net deferred tax assets/(liabilities)	$ 0	$ 0

Insider Trading Arrangements	12 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Insider Trading Arr Line Items
Material Terms of Trading Arrangement [Text Block]	Item *9B.* Other Information None.
Rule 10b5-1 Arrangement Adopted [Flag]	false
Non-Rule 10b5-1 Arrangement Adopted [Flag]	false
Rule 10b5-1 Arrangement Terminated [Flag]	false
Non-Rule 10b5-1 Arrangement Terminated [Flag]	false

Note 4 - Balance Sheet Components - Intangible Assets, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Less: Accumulated amortization	$ (6,099)	$ (5,434)
Finite-Lived Intangible Assets, Net	1,886	2,551
Acquired Patents and Licenses [Member]
Acquired patents and licenses	$ 7,985	$ 7,985

Note 2 - Summary of Significant Accounting Policies - Warrant Accrual Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Beginning balance	$ 50	$ 80
Add: Accruals for warranties issued during the period	0	42
Less: Adjustment for inventory at cost and excessive and obsolete inventory	(50)	(72)
Ending balance	$ 0	$ 50

Note 3 - Investments and Fair Value of Financial Instruments - Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Total assets measured at fair value	$ 41,184	$ 57,973
Total assets measured at fair value	(41,184)	(57,973)
Fair Value, Inputs, Level 1 [Member]
Total assets measured at fair value	41,184	57,973
Total assets measured at fair value	(41,184)	(57,973)
Fair Value, Inputs, Level 2 [Member]
Total assets measured at fair value	(0)	(0)
Total assets measured at fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Total assets measured at fair value	0	0
Total assets measured at fair value	0	0
Money Market Funds [Member]
Cash and Cash equivalents	41,184	57,973
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and Cash equivalents	41,184	57,973
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and Cash equivalents	0	0
Money Market Funds [Member] \| Fair Value, Inputs, Level 3 [Member]
Cash and Cash equivalents	$ 0	$ 0

Note 8 - Controlled Launch

12 Months Ended

Dec. 31, 2023

Notes to Financial Statements

Controlled Launch [Text Block]

8. Controlled Launch

In February 2021, the Company received 510(k) clearance from the FDA for its proprietary CellFX System for dermatologic procedures requiring ablation and resurfacing of the skin. In January 2021, the Company received CE marking approval for the CellFX System, which allows for marketing of the system in the EU for treatment of general dermatologic conditions, including SH, SK, and cutaneous non-genital warts. Additionally, in June 2021 the Company received Health Canada approval for the CellFX System, which allows for marketing of the system in Canada for use in dermatological procedures requiring ablation and resurfacing of the skin for the reduction, removal, and/or clearance of cellular-based benign lesions. In February 2021, the Company commenced a controlled launch of the CellFX System in the United States and European Union via its CellFX Expectations Excelled Program (the “Controlled Launch”). Subsequent to receiving Health Canada approval in June 2021, the Company also commenced its Controlled Launch in Canada.

As part of the Controlled Launch, the Company selected 70 physicians and their practices to be the first physician consultants to launch the CellFX System and the associated CellFX commercial procedures into their respective markets and geographies. In the Controlled Launch program, the Company provided and set up a CellFX System at each physician site and provided the physician with the necessary related products and components, free of charge, to complete the requirements of the Controlled Launch program. Each CellFX System and any unused component products remained the property of the Company throughout the Controlled Launch program. Under the Controlled Launch program, each physician was to identify and recruit up to 40 or 50 patients, depending on the contract, for participation in the Controlled Launch, performing a CellFX procedure on each of the appropriately selected patients. The physician and their patients completed evaluation surveys about their experiences with the CellFX System and provided other information helpful to the Company. Upon completion of the procedures and the survey feedback, the physician earned credits to be used towards the future purchase of the CellFX System or, in some jurisdictions, fair payment for their time and effort completing the paperwork required under the Controlled Launch program. Credits earned and, if applicable, any other payments earned were limited to a maximum amount dependent on the number of surveys received by the Company. Upon completion of the Controlled Launch program requirements, each physician could choose to enter into a purchase agreement with the Company, under which the physician could use the credits earned (or other payments earned, as applicable) towards the purchase of the already-delivered CellFX System, or the physician could return the CellFX System to the Company.

As patient procedures and surveys were completed under the Controlled Launch program, the Company accrued the value of the credits earned, which were recorded in accrued expenses, with a corresponding charge to sales and marketing expense. The Company did not record any sales and marketing expense in relation to the Controlled Launch program for the year ended December 31, 2023. The Company recorded an expense of $0.6 million for the year ended December 31, 2022. This expense was partially offset by $0.5 million of expense reversal for the return of certain CellFX Systems, resulting in a $0.1 million net sales and marketing expense in relation to the Controlled Launch.

In September 2022, the Company concluded the Controlled Launch program and notified all remaining program participants. In accordance with the Controlled Launch program, physicians having completed the program requirements could elect to purchase their already delivered CellFX System, applying credits earned, or return the CellFX System to the Company. The Company concluded these efforts in the fourth quarter of 2022 and has discontinued sales of the CellFX System, although the Company continues to offer its disposable treatment tips to dermatologists who have chosen to retain their existing CellFX consoles.

During the year ended December 31, 2023, the Company did not recognize any revenue in relation to the Controlled Launch program. During the year ended December 31, 2022, certain consultants completed the Controlled Launch program and entered into purchase agreements with the Company, whereby they used their credits or other earned payments towards the purchase of a CellFX System. Accordingly, approximately $0.4 million of the accrued liability related to the Controlled Launch program was relieved and recognized as revenue on a non-cash basis as a result of these purchases during the year ended December 31, 2022. See Note 9 for additional detail of revenue transactions.