Note 6 - Stockholders' Equity (Details Textual) - USD ($)		2 Months Ended	3 Months Ended
	Jan. 13, 2022	Mar. 31, 2022	Mar. 31, 2022	Mar. 31, 2021	Feb. 03, 2022
Proceeds from Issuance of Common Stock, Net			$ 594,000	$ 6,832,000
The 2016 Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)	392,500
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Additional Shares Authorized (in shares)	1,200,000
At The Market Offering Agreement [Member]
Additional Common Stock, Shares Authorized					$ 4,275,000
Stock Issued During Period, Shares, New Issues (in shares)		918,093
Proceeds from Issuance of Common Stock		$ 681,000
Shares Issued, Average Price Per Share (in dollars per share)		$ 0.74
Proceeds from Issuance of Common Stock, Net		$ 594,000
Payments of Stock Issuance Costs		$ 87,000
Minimum [Member] | At The Market Offering Agreement [Member]
Maximum Offering Price for Issuance of Common Stock					15,280,313
Maximum [Member] | At The Market Offering Agreement [Member]
Maximum Offering Price for Issuance of Common Stock					$ 19,555,261