CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows From Operating Activities:
Net loss	$ (7,950)	$ (7,600)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	902	874
Depreciation and amortization of property and equipment	491	549
Amortization of patents and other intangiable assets	434	618
Changes in fair value of earnout, derivative and warrant liabilities	96	(129)
Amortization of senior debt issuance costs and discounts	465	357
Amortization of short-term investment purchase discounts	(23)	(16)
Gain on sale of equipment		(1)
Other adjustments	(6)
Changes in operating assets and liabilities:
Accounts receivable	5,781	4,579
Inventories	792	(909)
Other assets	1,186	1,477
Accounts payable	6,500	(4,178)
Accrued expenses	(9,630)	(1,700)
Operating lease liabilities	(37)	(24)
Net cash used in operating activities	(999)	(6,103)
Cash Flows From Investing Activities:
Purchases of short-term investments	(2,992)	(7,190)
Sales and maturities of short-term investments	7,087
Capital expenditures	(160)	(167)
Intangible asset expenditures	(30)	(18)
Net cash provided by (used in) investing activities	3,905	(7,375)
Cash Flows From Financing Activities:
Proceeds from the issuance of common stock, net of issuance costs		11
Payments made on borrowings	(326)	(250)
Proceeds from short-term line of credit	22,500
Payments made on short-term line of credit	(13,931)
Payment of debt financing costs	(119)
Payment of payroll taxes withheld for releases of restricted stock units	(2)	(1)
Net cash provided by (used in) financing activities	8,122	(240)
Increase (decrease) in cash and cash equivalents	11,028	(13,718)
Cash and Cash Equivalents:
Beginning	16,830	46,478
Ending	27,858	32,760
Supplemental Cash Flow Information:
Interest paid	$ 1,503	$ 1,764