Note 9 - Stockholders' Equity, Stock Options and Warrants - Summary of Status of Options and Warrants Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Shares, options (in shares)	47,664
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 21.52	$ 22.6	$ 33.2
Shares, warrants (in shares)	1,806,589	1,816,437	1,584,995
Shares, warrants (in shares)	1,806,589	1,816,437	1,584,995
Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 14
Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	200
Stock Options One [Member]
Share-Based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in dollars per share)	3.44
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in dollars per share)	$ 14.65
Shares, options (in shares)	12,029
Weighted average remaining life, options (Year)	6 years 8 months 1 day
Stock Options Two [Member]
Share-Based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in dollars per share)	$ 16.28
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in dollars per share)	$ 29.4
Shares, options (in shares)	4,935
Weighted average remaining life, options (Year)	7 years 6 months 25 days
Stock Options Three [Member]
Share-Based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in dollars per share)	$ 30.8
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in dollars per share)	$ 52.2
Shares, options (in shares)	16,049
Weighted average remaining life, options (Year)	4 years 1 month 17 days
Stock Options Four [Member]
Share-Based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit (in dollars per share)	$ 101
Share-Based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit (in dollars per share)	$ 69,375
Shares, options (in shares)	14,651
Weighted average remaining life, options (Year)	3 years 6 months 7 days
Warrant One [Member]
Shares, warrants (in shares)	1,168,465
Weighted average remaining life, warrants (Year)	3 years 7 months 13 days
Shares, warrants (in shares)	1,168,465
Warrant One [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 14
Warrant One [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 20
Warrant Two [Member]
Shares, warrants (in shares)	368,246
Weighted average remaining life, warrants (Year)	2 years 21 days
Shares, warrants (in shares)	368,246
Warrant Two [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 21.05
Warrant Two [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 30
Warrant Three [Member]
Shares, warrants (in shares)	180,314
Weighted average remaining life, warrants (Year)	5 years 10 months 13 days
Shares, warrants (in shares)	180,314
Warrant Three [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 34.38
Warrant Three [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 40
Warrant Four [Member]
Shares, warrants (in shares)	89,564
Weighted average remaining life, warrants (Year)	1 year 9 months 29 days
Shares, warrants (in shares)	89,564
Warrant Four [Member] | Minimum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 43.75
Warrant Four [Member] | Maximum [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 200