Summary of Significant Accounting Policies - Summary of Revenue Disaggregated by Type and Geography (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 8,531	$ 24,102
Systems
Disaggregation of Revenue [Line Items]
Total revenues	5,549	18,749
Instruments and Accessories
Disaggregation of Revenue [Line Items]
Total revenues	1,555	4,519
Services
Disaggregation of Revenue [Line Items]
Total revenues	1,427	834
U.S
Disaggregation of Revenue [Line Items]
Total revenues	536	3,778
U.S | Systems
Disaggregation of Revenue [Line Items]
Total revenues	90	2,556
U.S | Instruments and Accessories
Disaggregation of Revenue [Line Items]
Total revenues	108	967
U.S | Services
Disaggregation of Revenue [Line Items]
Total revenues	338	255
Outside of U.S
Disaggregation of Revenue [Line Items]
Total revenues	7,995	20,324
Outside of U.S | Systems
Disaggregation of Revenue [Line Items]
Total revenues	5,459	16,193
Outside of U.S | Instruments and Accessories
Disaggregation of Revenue [Line Items]
Total revenues	1,447	3,552
Outside of U.S | Services
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,089	$ 579