Condensed Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net loss	$ (15,147)	$ (12,913)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	557	629
Amortization of operating lease right-of-use assets	342
Stock-based compensation expense	2,033	1,381
Change in fair value of derivative instrument	83	(142)
Non-cash interest expense	568	560
Deferred rent		(52)
Changes in operating assets and liabilities:
Accounts receivable	13	(115)
Prepaid expenses and other assets	(401)	145
Inventories	(141)	64
Accounts payable	(126)	132
Accrued expenses and other liabilities	118	(682)
Deferred revenue	(31)	(749)
Operating lease liabilities	(735)
Net cash used in operating activities	(12,867)	(11,742)
Cash flows from investing activities
Purchases and manufacture of property and equipment	(194)	(56)
Net cash used in investing activities	(194)	(56)
Cash flows from financing activities
Proceeds from issuance of common stock and stock option exercises, net		4
Principal repayments of finance leases	(344)	(352)
Net cash used in financing activities	(344)	(348)
Net decrease in cash, cash equivalents and restricted cash	(13,405)	(12,146)
Cash, cash equivalents and restricted cash at beginning of period	50,985	42,059
Cash, cash equivalents and restricted cash at end of period	37,580	29,913
Supplemental disclosures of cash flow information
Cash paid for interest	1,131	972
Supplemental disclosures of noncash activities
Transfer of T2 owned instruments and components to (from) inventory	(154)	802
Change in fair value of warrants issued upon modification	147
Right-of-use assets obtained in exchange for new operating lease liabilities	4,805
Purchases of property and equipment included in accounts payable and accrued expenses	$ 56	$ 119