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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue	$ 655	$ 3,639	$ 1,255	$ 5,820
Systems [Member]
Revenue	162	2,782	202	4,065
Instruments and Accessories [Member]
Revenue	153	560	355	1,106
Service [Member]
Revenue	340	297	698	649
UNITED STATES
Revenue	155	152	313	285
UNITED STATES | Systems [Member]
Revenue	45	0	75	0
UNITED STATES | Instruments and Accessories [Member]
Revenue	7	25	67	25
UNITED STATES | Service [Member]
Revenue	103	127	171	260
Non-US [Member]
Revenue	500	3,487	942	5,535
Non-US [Member] | Systems [Member]
Revenue	117	2,782	127	4,065
Non-US [Member] | Instruments and Accessories [Member]
Revenue	146	535	288	1,081
Non-US [Member] | Service [Member]
Revenue	$ 237	$ 170	$ 527	$ 389