CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 3,501	$ 3,868
Accounts receivable	1,505	1,681
Inventories	1,900	1,766
Prepaid expenses and other	1,255	1,347
Total current assets	8,161	8,662
Property and equipment, net	658	827
Goodwill	13,276	13,276
Intangible assets, net	84	111
Other	262	263
Total assets	22,441	23,139
Current liabilities
Accounts payable	233	170
Deferred revenue	2,702	3,938
Accrued expenses and other	1,886	2,507
Total current liabilities	4,821	6,615
Long-term liabilities	18	18
Convertible notes payable	9,635	9,160
Total liabilities	14,474	15,793
Commitments and contingencies (Note 4)
Stockholders’ equity
Preferred stock, $0.01 par value; 20,000 shares authorized; none issued and outstanding
Common stock, $0.001 par value; 120,000 shares authorized; 8,171 shares and 8,068 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively	8	8
Additional paid-in capital	232,069	232,026
Accumulated deficit	(224,110)	(224,688)
Total stockholders’ equity	7,967	7,346
Total liabilities and stockholders’ equity	$ 22,441	$ 23,139

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.