Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net (loss) income	$ (2,060)	$ 5,951	$ (1,496)
Reconciliation of net income to net cash provided by (used in) operating activities:
Depreciation and amortization	2,253	1,899	1,911
Share-based compensation expense	1,469	1,201	1,750
Changes in operating assets and liabilities:
Accounts receivable	2,178	192	(2,499)
Inventories	(704)	(1,998)	(424)
Prepaid expenses and other current assets	(1,849)	64	259
Other non-current assets	17	18	(89)
Accounts payable	183	1,585	(925)
Accrued expenses	225	1,214	1,591
Deferred revenue	455	1,033	(1,038)
Other long-term liabilities	(40)	27	69
Net cash provided by (used in) operating activities	2,127	11,186	(891)
Investing activities:
Purchase of property and equipment	(2,840)	(3,564)	(1,708)
Net cash used in investing activities	(2,840)	(3,564)	(1,708)
Financing activities:
Proceeds from exercise of stock options			82
Proceeds from loan facility	954
Proceeds from equipment loans	1,501
Principal payments on debt	(1,402)	(226)	(238)
Payments for the purchase of treasury stock			(22)
Dividends paid	(14)	(28)	(28)
Net cash provided by (used in) financing activities	1,039	(254)	(206)
Effect of exchange rate changes on cash and cash equivalents	126	(275)	(56)
Net increase (decrease) in cash and cash equivalents	452	7,093	(2,861)
Cash and cash equivalents, beginning of period	20,994	13,901	16,762
Cash and cash equivalents, end of period	21,446	20,994	13,901
Supplemental cash flow information
Cash paid for interest	115	85	101
Cash paid for income taxes	76		2
Supplemental noncash investing
Purchases of equipment through accounts payable and accrued expenses	320	$ 460	$ 95
Series C Preferred Stock [Member]
Supplemental noncash investing
Gain on conversion of Series C Preferred Stock	$ 459