Note 3 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Restricted cash held as a certificate of deposit	$ 476	$ 476
Warrant liabilities	232	334
Embedded derivative liability	159
Total liabilities	391
Fair Value, Inputs, Level 1 [Member]
Restricted cash held as a certificate of deposit	476	476
Warrant liabilities	0	0
Embedded derivative liability	0
Total liabilities	0
Fair Value, Inputs, Level 2 [Member]
Restricted cash held as a certificate of deposit	0	0
Warrant liabilities	232	334
Embedded derivative liability	159
Total liabilities	391
Fair Value, Inputs, Level 3 [Member]
Restricted cash held as a certificate of deposit	0	0
Warrant liabilities	0	$ 0
Embedded derivative liability	0
Total liabilities	$ 0