Note 2 - Summary of Significant Accounting Policies - Revenue Disaggregated by Type and Geography (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue	$ 1,102	$ 655	$ 3,185	$ 1,255
Systems [Member]
Revenue	349	162	1,614	202
Instruments and Accessories [Member]
Revenue	347	153	786	355
Service [Member]
Revenue	406	340	785	698
UNITED STATES
Revenue	274	155	527	313
UNITED STATES | Systems [Member]
Revenue	91	45	184	75
UNITED STATES | Instruments and Accessories [Member]
Revenue	79	7	141	67
UNITED STATES | Service [Member]
Revenue	104	103	202	171
Non-US [Member]
Revenue	828	500	2,658	942
Non-US [Member] | Systems [Member]
Revenue	258	117	1,430	127
Non-US [Member] | Instruments and Accessories [Member]
Revenue	268	146	645	288
Non-US [Member] | Service [Member]
Revenue	$ 302	$ 237	$ 583	$ 527