CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net loss	$ (8,137)	$ (17,286)	$ (19,566)
Adjustments to reconcile net loss to net cash used for operating activities:
Depreciation and amortization	1,426	1,612	1,886
Impairment of intangible asset	0	0	2,638
Stock compensation expense	7,223	2,680	2,499
Change in fair value of warrants	2,524	257	0
Loss on extinguishment of debt	838	860	0
Foreign currency translation loss	51	37	5
Gain (loss) on sale of fixed assets	22	(115)	0
Amortization of premiums and discounts on marketable securities	(327)	0	0
Changes in operating assets and liabilities:
Inventory	235	(305)	(2,108)
Deferred rent	(247)	785	1,568
Accounts receivable	(5,184)	(1,177)	(6,174)
Prepaid and other current assets	(1,267)	(261)	(701)
Accounts payable	899	(1,361)	(1,076)
Accrued expenses	1,493	1,050	920
Other non-current assets and liabilities, net	39	41	217
Net cash used for operating activities	(412)	(13,183)	(19,892)
Investing activities:
Purchases of short term investments	(66,549)	0	0
Sales and maturities of short term investments	2,200	0	0
Expenditures for property, plant and equipment	(2,678)	(1,510)	(1,415)
Net cash used for investing activities	(67,027)	(1,510)	(1,415)
Financing activities:
Net proceeds from equity offering	70,028	0	0
Net proceeds from issuance of common stock	4,361	8,220	19,455
Deferred financing costs	0	(30)	(213)
Proceeds from exercise of warrants	2,716	4,010	0
Borrowings under revolving and term loan credit agreements	0	14,793	12,710
Warrants issued in connection with debt arrangement	0	207	190
Payments on term loan credit agreement	0	(889)	(2,400)
Payments on long-term debt	(17,532)	(7,151)	(38)
Fee on long-term debt	(710)	(583)	0
Net cash provided by (used in) financing activities	58,863	18,577	29,704
Net increase (decrease) in cash	(8,576)	3,884	8,397
Cash at beginning of period	26,862	22,978	14,581
Cash at end of period	18,286	26,862	22,978
Supplemental cash flow information (non-cash):
Shares exchanged between common and preferred stock	0	38,389	3,150
Additions to equipment in process included in accounts payable	$ 606	$ 341	$ 18