Note 4 - Warrants (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Aug. 31, 2021	Apr. 30, 2021
Share-Based Payment Arrangement, Expense	$ 514,000	$ 433,000	$ 1,041,000	$ 838,000
Equity Classified Warrants [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)	50,000		50,000			250,000	71,500
Warrants and Rights Outstanding, Term (Year)	10 years		10 years			10 years	5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 1.49		$ 1.49			$ 3.08	$ 3.63
Class of Warrant or Right, Outstanding (in shares)	446,502		446,502		396,502
Class of Warrant or Right, Vested and Exercisable (in shares)	193,710		193,710		186,560
Share-Based Payment Arrangement, Expense	$ 83,000	$ 11,000	$ 166,000	$ 11,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 451,000		$ 451,000