Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating Activities
Net loss	$ (7,479)	$ (4,777)
Adjustments to reconcile net loss to net cash and cash equivalents used in operating activities:
Depreciation and amortization	286	352
Amortization of debt issuance costs	22	27
Stock-based compensation	405	65
Changes in operating assets and liabilities:
Accounts receivable	136	281
Interest receivable	(5)	16
Inventory	50	(109)
Other current and long term assets	(178)	(52)
Restricted cash	125
Accounts payable	54	410
Accrued expenses	125	192
Net cash and cash equivalents used in operating activities	(6,459)	(3,595)
Investing Activities
Proceeds from sale and maturities of investments	1,722	907
Purchase of property and equipment	(187)	(69)
Net cash and cash equivalents provided by investing activities	1,535	838
Financing Activities
Payment of debt	(938)
Proceeds from exercise of stock options	8
Net cash and cash equivalents used in financing activities	(930)
Net decrease in cash and cash equivalents	(5,854)	(2,757)
Cash and Cash Equivalents, beginning of period	10,014	8,896
Cash and Cash Equivalents, end of period	4,160	6,139
Supplemental Disclosure for Cash Flow Information
Interest paid	$ 179	$ 190