Note 7 - Stockholders' Equity (Details Textual) - USD ($)					3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 21, 2023	Apr. 12, 2022	Mar. 29, 2021	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Proceeds from Issuance of Common Stock							$ 2,950,000	$ 1,519,000
Payments of Stock Issuance Costs							$ 285,000	$ 165,000
Underwriters [Member]
Stock Issued During Period, Shares, New Issues (in shares)				80,000
June 2023 Financing [Member]
Stock Issued During Period, Shares, New Issues (in shares)		1,133,141
Shares Issued, Price Per Share (in dollars per share)		$ 2.336
Proceeds from Issuance of Common Stock		$ 2,600,000
Payments of Stock Issuance Costs		$ 177,000
June 2023 Financing [Member] | Company’s Directors and Executive Officers [Member]
Stock Issued During Period, Shares, New Issues (in shares)		203,337
Sales Agreement with Cantor Fitzgerald Co (Cantor) [Member]
Stock Issued During Period, Shares, New Issues (in shares)					28,599	575,000	134,840
Proceeds from Issuance of Common Stock					$ 58,000	$ 1,500,000	$ 302,000
Payments of Stock Issuance Costs					$ 29,000	$ 232,000	$ 42,000
Sale of Stock, Aggregate Value, Maximum	$ 8,400,000		$ 10,500,000
Accrued Sales Commission, Current, Percentage			3.00%
Purchase Agreement with Lincoln Park [Member]
Stock Issued During Period, Shares, New Issues (in shares)				373,832
Shares Issued, Price Per Share (in dollars per share)				$ 5.35
Proceeds from Issuance of Common Stock				$ 2,000,000
Sale of Stock, Aggregate Value, Maximum				$ 20,000,000
Stock Issuable, Commitment Shares on Pro Rata Basis				5,000