Condensed Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Accounts receivable, allowance for doubtful accounts	$ 9	$ 6
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	56,451	56,451
Preferred stock, shares outstanding (in shares)	56,451	56,451
Preferred stock, liquidation preference	$ 56,366	$ 56,366
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	6,081,333	4,778,263
Common stock, shares outstanding (in shares)	6,081,333	4,778,263