Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 33,301	$ 37,495
Accounts receivable, net of allowance for doubtful accounts of $17 and $17, respectively	3	4
Inventory	544	571
Prepaid expenses and other current assets	1,078	1,279
Total current assets	34,926	39,349
Property and equipment, net of accumulated depreciation of $1,053 and $1,051, respectively	1,704	1,598
Intangible assets, net of accumulated amortization of $1,791 and $1,653, respectively	4,549	4,687
Total assets	41,179	45,634
Current liabilities:
Accounts payable	1,898	1,124
Accrued expenses	2,697	1,675
Deferred revenue	588	416
Warrant liability, current	851	278
Total current liabilities	6,034	3,493
Warrant liability, long term	12,098	11,008
Other long term liabilities	771	724
Total liabilities	18,903	15,225
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares outstanding	0	0
Common stock, $0.001 par value; 100,000,000 shares authorized; 40,888,065 and 40,856,815 shares issued and outstanding, respectively	41	41
Additional paid-in capital	143,478	143,086
Accumulated deficit	(121,243)	(112,718)
Total stockholders’ equity	22,276	30,409
Total liabilities and stockholders’ equity	$ 41,179	$ 45,634