Note 2 - Summary of Significant Accounting Policies - Revenue Disaggregated by Type and Geography (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue	$ 2,083	$ 600
Systems [Member]
Revenue	1,265	69
Instruments and Accessories [Member]
Revenue	439	173
Service [Member]
Revenue	379	358
UNITED STATES
Revenue	253	159
UNITED STATES | Systems [Member]
Revenue	93	30
UNITED STATES | Instruments and Accessories [Member]
Revenue	62	60
UNITED STATES | Service [Member]
Revenue	98	69
Non-US [Member]
Revenue	1,830	441
Non-US [Member] | Systems [Member]
Revenue	1,172	39
Non-US [Member] | Instruments and Accessories [Member]
Revenue	377	113
Non-US [Member] | Service [Member]
Revenue	$ 281	$ 289