Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (5,539)	$ (6,193)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,366	985
Depreciation and amortization	678	604
Other	67	63
Changes in operating assets and liabilities:
Accounts receivable	(10,799)	(608)
Inventories	(2,028)	(655)
Prepaid expenses and other assets	(1,364)	250
Contract assets	997	73
Accounts payable	4,137	550
Accrued expenses and other current liabilities	(25)	(99)
Deferred revenue	520	(999)
Net cash used in operating activities	(11,990)	(6,029)
Cash flows from investing activities:
Proceeds from sale of assets		2,750
Purchases of equipment, molds, furniture and fixtures	(391)	(61)
Additions to patent rights		(10)
Net cash (used in) provided by investing activities	(391)	2,679
Cash flows from financing activities:
Proceeds from issuance of common stock, net	7,785
Proceeds from exercise of stock options	350	28
Taxes paid related to net share settlement of equity awards	(408)	(130)
Net cash provided by (used in) financing activities	7,727	(102)
Effect of exchange rate changes on cash		1
Net decrease in cash and cash equivalents	(4,654)	(3,451)
Cash and cash equivalents:
Beginning of period	27,892	26,562
End of period	23,238	23,111
Supplemental disclosure of non-cash investing activities:
Purchases of equipment, molds, furniture and fixtures recorded in accounts payable and accrued expenses	$ 399	173
Additions to patent rights recorded in accounts payable and accrued expenses		$ 6