Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Operating activities
Net loss	$ (12,754)	$ (7,181)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	901	974
Amortization of debt discount	110	95
Stock-based compensation	488	417
Revaluation of preferred stock warrant liability	(1,156)	(97)
Interest accrued on long-term notes	99	32
Loss on disposal of property and equipment	1
Changes in operating assets and liabilities
Accounts receivable	(1,457)	(590)
Inventory	(247)	(602)
Prepaid expenses and other	(1,213)	10
Other assets	(131)	(11)
Accounts payable	826	(79)
Accrued liabilities	329	321
Deferred revenue	335	(102)
Deferred rent	(373)	(347)
Net cash used in operating activities	(14,242)	(7,160)
Investing activities
Purchases of property and equipment	(254)	(222)
Increase in restricted cash		(1)
Net cash used in investing activities	(254)	(223)
Financing activities
Proceeds from issuance of long-term debt	5,000	7,500
Repayment of long-term debt	(109)	(1,603)
Deferred offering costs	(1,705)
Proceeds from exercise of stock options	373	30
Net cash provided by financing activities	3,559	5,927
Net decrease in cash and cash equivalents	(10,937)	(1,456)
Cash and cash equivalents
Beginning of period	21,692	10,868
End of period	$ 10,755	$ 9,412