CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Unaudited - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (13,465)	$ (24,239)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	616	659
Amortization of investment discount	54	49
Equity-based compensation	2,979	8,839
Amortization of debt discount and issuance costs	162	2,996
Loss on disposal of property and equipment	152	0
Gain on extinguishment of debt	(3,366)	0
(Increase) decrease in assets:
Contributions to deferred compensation plan	(5)	(112)
Accounts receivable	206	(401)
Inventory	(653)	(683)
Prepaid expense and other	(714)	(292)
Increase (decrease) in liabilities:
Accounts payable	1,154	575
Accrued liabilities	1,081	183
Accrued interest	(751)	(1,048)
Deferred revenue and income	(53)	(19)
Deferred compensation	(3)	118
Net cash used in operating activities	(12,606)	(13,375)
Cash flows from investing activities:
Purchases of equipment	(447)	0
Purchase of marketable securities	(24,144)	(7,307)
Maturities of marketable securities	10,950	15,829
Net cash (used in) provided by investing activities	(13,641)	8,522
Cash flows from financing activities:
Proceeds from issuance of common stock	0	10,666
Proceeds from exercise of options	0	1,109
Proceeds from issuance of common stocks under employee purchase plan	77	80
Net cash provided by financing activities	77	11,855
Effect of exchange rate on cash	(74)	(57)
(Decrease) increase in cash and cash equivalents	(26,244)	6,945
Cash and cash equivalents, beginning of period	39,898	35,781
Cash and cash equivalents, end of period	13,654	42,726
Non-cash investing activities:
Net transfer of instruments from inventory to property and equipment	220	306
Supplemental cash flow information:
Interest paid	1,506	2,144
Extinguishment of Convertible Senior Notes through issuance of common stock	$ 1,258	$ 0