Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Estimated Lives of Assets

Depreciation is recorded using the straight-line method over the estimated useful lives of the assets as follows:

Machinery, manufacturing and    demonstration equipment	3-5 years
Computer equipment	3 years
Furniture	5 years
Leasehold improvements	Lesserof lease term or 3 to 10 years

Summary of Revenue Disaggregated by Type and Geography

The following table presents revenue disaggregated by type and geography:

	Year Ended
	December 31,
	2018		2017		2016
	(in thousands)
U.S.
Systems	$	2,556	$	865	$	—
Instruments and accessories		967		390		—
Services		255		—		—
Total U.S. revenue		3,778		1,255		—
Outside of U.S. ("OUS")
Systems		16,193		4,198		1,445
Instruments and accessories		3,341		1,080		—
Services		790		578		74
Total OUS revenue		20,324		5,856		1,519
Total
Systems		18,749		5,063		1,445
Instruments and accessories		4,308		1,470		—
Services		1,045		578		74
Total revenue	$	24,102	$	7,111	$	1,519