Note 9 - Stockholders' Equity, Stock Options and Warrants - Summary of Transactions for Stock Options and Warrants (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Warrants, outstanding (in shares)	1,816,437	1,584,995
Warrants, average exercise price (in dollars per share)	$ 22.6	$ 33.2
Warrants, issued (in shares)	0	1,053,136
Issued, average exercise price, warrants (in dollars per share)	$ 0	$ 14
Warrants, forfeited (in shares)	0	0
Warrants, expired (in shares)	(9,848)	(5,422)
Expired, average exercise price, warrants (in dollars per share)	$ 219.6	$ 329.6
Cancelled (in dollars per share)		$ 0
Warrants, cancelled (in shares)		(816,272)
Cancelled, average exercise price, warrants (in dollars per share)		$ 30.2
Number of Shares Outstanding (in shares)	47,664
Average Exercise Price Outstanding (in dollars per share)	$ 82.23
Warrants, outstanding (in shares)	1,806,589	1,816,437
Warrants, average exercise price, warrants (in dollars per share)	$ 21.52	$ 22.6
Share-Based Payment Arrangement, Option [Member]
Number of Shares Outstanding (in shares)	49,053	53,144
Average Exercise Price Outstanding (in dollars per share)	$ 91.6	$ 96.6
Number of Shares Issued (in shares)	1,075	1,599
Average Exercise Price Issued (in dollars per share)	$ 5.45	$ 8.4
Number of Shares Forfeited (in shares)	(49)	(2,013)
Average Exercise Price Forfeited (in dollars per share)	$ 6.18	$ 17.6
Number of Shares Expired (in shares)	(2,415)	(3,677)
Average Exercise Price Expired (in dollars per share)	$ 139.3	$ 208.4
Number of Shares Outstanding (in shares)		49,053
Average Exercise Price Outstanding (in dollars per share)		$ 91.6