Note 5 - Accrued Liabilities - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued bonuses	$ 786	$ 744
Accrued payroll and other related expenses	435	473
Deferred revenue - subscription rental program	436	345
Accrued clinical trial costs	361	91
Accrued professional fees	119	290
Accrued sales commission	43	37
Accrued inventory	0	87
Other accruals	163	217
Total accrued liabilities	2,557	2,416	[1]
Accrued Liabilities [Member]
Current operating lease liabilities	$ 214	$ 132

[1] The condensed consolidated balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements as of that date.