Note 2 - Summary of Significant Accounting Policies - Revenue Disaggregated by Type and Geography (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue	$ 2,571	$ 814	$ 5,756	$ 2,068
Systems [Member]
Revenue	1,410	232	3,024	433
Instruments and Accessories [Member]
Revenue	766	204	1,552	559
Service [Member]
Revenue	395	378	1,180	1,076
UNITED STATES
Revenue	243	289	770	603
UNITED STATES | Systems [Member]
Revenue	78	101	262	176
UNITED STATES | Instruments and Accessories [Member]
Revenue	60	82	201	149
UNITED STATES | Service [Member]
Revenue	105	106	307	278
Non-US [Member]
Revenue	2,328	525	4,986	1,465
Non-US [Member] | Systems [Member]
Revenue	1,332	131	2,762	257
Non-US [Member] | Instruments and Accessories [Member]
Revenue	706	122	1,351	410
Non-US [Member] | Service [Member]
Revenue	$ 290	$ 272	$ 873	$ 798