Note 6 - Stockholders' Equity, Stock Options and Warrants - Summary of Transactions for Stock Options and Warrants (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Number of Shares Outstanding (in shares)	1,816,437	1,584,995
Average Exercise Price Outstanding (in dollars per share)	$ 22.60	$ 33.20
Number of Shares Issued (in shares)	0	1,053,136
Average Exercise Price Issued (in dollars per share)	$ 0	$ 14.00
Number of Shares Forfeited (in shares)	0	0
Expired, warrants (in shares)	(9,417)	(5,422)
Average Exercise Price Expired (in dollars per share)	$ 217.64	$ 329.60
Cancelled, warrants (in shares)		816,272
Cancelled, warrants, average exercise price (in dollars per share)		$ 30.20
Number of Shares Outstanding (in shares)	1,807,020	1,816,437
Average Exercise Price Outstanding (in dollars per share)	$ 21.58	$ 22.60
Share-Based Payment Arrangement, Option [Member]
Number of Shares Outstanding (in shares)	49,053	53,144
Average Exercise Price Outstanding (in dollars per share)	$ 91.69	$ 96.60
Number of Shares Issued (in shares)	1,075	1,599
Average Exercise Price Issued (in dollars per share)	$ 5.45	$ 8.40
Number of Shares Forfeited (in shares)	(49)	(2,013)
Average Exercise Price Forfeited (in dollars per share)	$ 6.18	$ 17.60
Expired, options (in shares)	(1,854)	(3,677)
Expired, options, average exercise price (in dollars per share)	$ 121.24	$ 208.40
Cancelled, options (in shares)		0
Cancelled, options, average exercise price (in dollars per share)		$ 0
Number of Shares Outstanding (in shares)	48,225	49,053
Average Exercise Price Outstanding (in dollars per share)	$ 83.58	$ 91.69