Note 3 - Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenue	$ 1,066	$ 2,083
UNITED STATES
Revenue	251	253
Non-US [Member]
Revenue	815	1,830
Systems [Member]
Revenue	0	924
Systems [Member] | UNITED STATES
Revenue	0	3
Systems [Member] | Non-US [Member]
Revenue	0	921
Instruments and Accessories [Member]
Revenue	347	439
Instruments and Accessories [Member] | UNITED STATES
Revenue	64	62
Instruments and Accessories [Member] | Non-US [Member]
Revenue	283	377
Service [Member]
Revenue	308	379
Service [Member] | UNITED STATES
Revenue	74	98
Service [Member] | Non-US [Member]
Revenue	234	281
Lease [Member]
Revenue	411	341
Lease [Member] | UNITED STATES
Revenue	113	90
Lease [Member] | Non-US [Member]
Revenue	$ 298	$ 251