Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Sales:
Sales	$ 13,149	$ 7,223	$ 23,723	$ 12,263
Cost of sales:
Cost of sales	6,236	3,539	11,044	5,950
Gross profit	6,913	3,684	12,679	6,313
Operating expenses:
Selling, general and administrative expenses	13,460	11,186	25,593	21,991
Research, development and engineering costs, net	4,226	3,221	7,506	7,594
Total operating expenses	17,686	14,407	33,099	29,585
Operating loss	(10,773)	(10,723)	(20,420)	(23,272)
Interest expense, net	936	398	1,786	768
Other expense, net	54	117	77	320
Loss before provision for income taxes	(11,763)	(11,238)	(22,283)	(24,360)
Provision for income taxes	15		28
Net loss	(11,778)	(11,238)	(22,311)	(24,360)
Other comprehensive gain:
Unrealized holding gain on investments arising during period		2	1	2
Other comprehensive gain		2	1	2
Comprehensive loss	$ (11,778)	$ (11,236)	$ (22,310)	$ (24,358)
Basic and diluted net loss per share (in dollars per share)	$ (0.83)	$ (1.07)	$ (2.04)	$ (2.34)
Basic and diluted weighted average shares outstanding (in shares)	14,209	10,458	10,922	10,396
Product [Member]
Sales:
Sales	$ 12,755	$ 6,665	$ 22,873	$ 11,253
Cost of sales:
Cost of sales	5,762	3,273	10,216	5,374
Service [Member]
Sales:
Sales	394	558	850	1,010
Cost of sales:
Cost of sales	$ 474	$ 266	$ 828	$ 576