Note 5 - Warrants (Details Textual) - USD ($)	1 Months Ended		12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Aug. 31, 2023	Jun. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Warrant Liabilities, Transaction Costs			$ 510,000	$ (0)
Class of Warrant or Right, Outstanding (in shares)		1,372,157	1,372,157	220,192
Share-Based Payment Arrangement, Expense			$ 1,984,000	$ 2,275,000
The 2023 Securities Purchase Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)		240,151
Proceeds from Issuance or Sale of Equity		$ 4,500,000
Warrants Issued in June 2018 and Expiring December 22, 2023 [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)									7,892
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)									$ 181.8
Warrants Issued in June 2018 and Expiring June 21, 2023 [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)									365
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)									$ 208.8
Warrants to Purchase Common Stock [Member] | Subsequent Event [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	3,334
Class of Warrant or Right, Expiration Period (Year)	10 years
Class of Warrant or Right, Vesting Period (Year)	4 years
Pre-funded Warrants Member Issued In Connection With The 2023 Securities Purchase Agreement[Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		229,506	229,506
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 0.001	$ 0.001
Class of Warrant or Right, Outstanding (in shares)		229,506	229,506	0
Unregistered Warrants Issued In Connection With The 2023 Securities Purchase Agreement [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)		939,312	939,312
Common Warrants Issued In Connection With The 2023 Securities Purchase Agreement[Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 9.6	$ 9.6
Warrants and Rights Outstanding, Term (Year)		5 years	5 years
Combined Warrants Issued In Connection With The 2023 Securities Purchase Agreement [Member] | Institutional Investor [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 9.6	$ 9.6
Combined Warrants Issued In Connection With The 2023 Securities Purchase Agreement [Member] | Executive Officers, Employees, Advisors and the Board of Directors [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 10.35	$ 10.35
Equity Classified Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)					6,667	10,000	16,667	3,334
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)					$ 9.3	$ 9	$ 18.6	$ 22.35
Warrants and Rights Outstanding, Term (Year)					5 years	10 years	10 years	10 years
Class of Warrant or Right, Outstanding (in shares)		289,276	289,276	43,103
Class of Warrant or Right, Vested and Exercisable (in shares)		266,350	266,350	26,724
Share-Based Payment Arrangement, Expense			$ 196,000	$ 398,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 353,000	$ 353,000