Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Product revenue	$ 391	$ 97	$ 838	$ 119
Cost of product revenue	428	22	889	40
Gross profit (loss)	(37)	75	(51)	79
Expenses
Research and development	1,327	1,181	3,098	2,059
Sales and marketing	577	506	1,115	772
General and administrative	1,509	1,432	3,449	2,718
Total expenses	3,413	3,119	7,662	5,549
Operating loss	(3,450)	(3,044)	(7,713)	(5,470)
Interest and other income (expense)
Interest expense, net	0	0	0	(1)
Change in fair value of warrants liabilities (expense)	(47)	4,925	1,123	(1,249)
Cease-use expense	0	0	(94)	0
Other expense	(16)	0	(18)	0
Inducement charge for Series C warrants	0	0	0	(3,050)
Interest and other income (expense), net	(63)	4,925	1,011	(4,300)
Net income (loss)	$ (3,513)	$ 1,881	$ (6,702)	$ (9,770)
Net income (loss) per common share:
Basic (in dollars per share)	$ (0.23)	$ 0.25	$ (0.44)	$ (1.35)
Diluted (in dollars per share)	$ (0.23)	$ 0.25	$ (0.44)	$ (1.35)
Weighted-average common shares outstanding used to calculate net income (loss) per common share:
Basic (in shares)	15,528,922	7,517,794	15,162,520	7,243,164
Diluted (in shares)	15,528,922	7,630,644	15,162,520	7,243,164