Note 6 - Accrued Liabilities - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Accrued bonuses	$ 744	$ 726
Accrued payroll and other related expenses	473	839
Deferred revenue - subscription rental program	345	662
Accrued professional fees	290	592
Accrued inventory	87	474
Accrued sales commission	37	281
Accrued interest	9	440
Other accruals	268	255
Total accrued liabilities	2,416	4,698	$ 6,996	$ 6,766
Customer Contracts Liabilites [Member]
Contract with customer, liability	17	108
Customer Advances [Member]
Contract with customer, liability	14	53
Accrued Liabilities [Member]
Current operating lease liabilities	$ 132	$ 268