Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net loss	$ (1,768)	$ (2,163)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	279	252
Stock-based compensation	182	281
Changes in operating assets and liabilities:
Trade accounts receivable	(4)	120
Inventory	(32)	(76)
Prepaid expenses and other current assets	52	94
Accounts payable and accrued liabilities	109	67
Deferred revenue	(3)	(6)
Net cash used in operating activities	(1,185)	(1,431)
Investing Activities:
Purchases of property and equipment	(184)	(47)
Net cash used in investing activities	(184)	(47)
Financing Activities:
Proceeds from exercise of stock options	11	42
Net cash provided by financing activities	11	42
Net decrease in cash and restricted cash	(1,358)	(1,436)
Cash and restricted cash at beginning of period	35,234	41,309
Cash and restricted cash at end of period	33,876	39,873
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Accrued capital expenditures	$ (36)