Note 2 - Summary of Significant Accounting Policies - Revenue Disaggregated by Type and Geography (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue	$ 3,175	$ 8,531
Systems [Member]
Revenue	772	5,549
Instruments and Accessories [Member]
Revenue	840	1,555
Service [Member]
Revenue	1,563	1,427
UNITED STATES
Revenue	849	536
UNITED STATES | Systems [Member]
Revenue	282	90
UNITED STATES | Instruments and Accessories [Member]
Revenue	187	108
UNITED STATES | Service [Member]
Revenue	380	338
Non-US [Member]
Revenue	2,326	7,995
Non-US [Member] | Systems [Member]
Revenue	490	5,459
Non-US [Member] | Instruments and Accessories [Member]
Revenue	653	1,447
Non-US [Member] | Service [Member]
Revenue	$ 1,183	$ 1,089