Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net loss	$ (6,702)	$ (9,770)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	55	31
Loss on disposition of property and equipment	1	0
Stock-based compensation expense	354	602
Change in fair value of common stock warrants	(1,123)	1,249
Inducement charge for Series C warrants	0	3,050
Change in fair value of contingent consideration	27	0
Change in operating assets and liabilities:
Accounts receivable	(132)	(12)
Inventory	(223)	(169)
Prepaid expenses and other assets	10	(59)
Accounts payable	334	401
Accrued compensation and other current liabilities	(689)	617
Other long-term liabilities	64	0
Net cash used in operating activities	(8,024)	(4,060)
Cash flows from investing activities:
Increase in restricted cash	0	(15)
Purchase of property and equipment	(39)	(16)
Net cash used in investing activities	(39)	(31)
Cash flows from financing activities:
Proceeds from sale of Series A preferred convertible stock	5,071	0
Initial public offering costs paid	0	(530)
Proceeds from exercise of common stock options	70	294
Repayment of credit line	0	(102)
Net cash provided by financing activities	5,070	3,664
Net decrease in cash and cash equivalents	(2,993)	(427)
Cash and cash equivalents, beginning of period	5,495	7,957
Cash and cash equivalents, end of period	2,502	7,530
Supplemental disclosures of noncash investing and financing information
Conversion of Series A preferred to common stock	2,220	0
Patent costs included in Accrued liabilities	0	450
Stock issuable in consideration for Patent purchase	0	112
Reduction in initial public offering costs payable	0	45
Cashless exercise of 2010/2012 warrants	0	13
Series A Convertible Preferred Stock [Member]
Cash flows from financing activities:
Initial public offering costs paid	(71)	0
Series A Warrant Liability [Member]
Cash flows from financing activities:
Proceeds upon exercise of warrants	0	156
Series A Warrant Liability [Member] | Cash Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	42
Private Placement Series B Warrants [Member]
Cash flows from financing activities:
Proceeds upon exercise of warrants	0	3,832
Tender Offer Series B Warrants [Member]
Cash flows from financing activities:
Proceeds upon exercise of warrants	0	189
Series B Warrant Liability [Member]
Cash flows from financing activities:
Series B warrant transaction costs paid	0	(175)
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	3
Series B Warrant transaction costs included in accounts payable	0	131
Series B Warrant Liability [Member] | Cash Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	6,748
Series B Warrant Liability [Member] | Cash Less Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	$ 593	$ 1,724