Condensed Consolidated Statement of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net loss	$ (4,175)	$ (5,558)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	498	264
Share-based compensation	697	506
Bad debt provision	29	(28)
Non-cash inventory adjustments	403	(636)
Changes in operating assets and liabilities:
Accounts receivable	(1,202)	72
Inventories	(1,531)	757
Other current assets	(116)	165
Accounts payable	129	(112)
Accrued compensation	(856)	(188)
Other liabilities	20	(738)
Net cash used in operating activities	(6,104)	(5,496)
Cash flows from investing activities
Restricted cash	249
Purchase of available-for-sale securities	(13,848)
Payments for intellectual property licenses	(345)	(739)
Purchases of property and equipment	(1,003)	(17)
Proceeds from sales of marketable securities	2,000
Maturity of short-term investment		5,000
Net cash (used in) provided by investing activities	(12,947)	4,244
Cash flows from financing activities
Principal repayment of borrowings	(287)	(267)
Proceeds from stock exercises	105
Net cash used in financing activities	(182)	(267)
Net decrease in cash and cash equivalents	(19,233)	(1,519)
Cash and cash equivalents at beginning of period	51,250	25,320
Cash and cash equivalents at end of period	32,017	23,801
Non-cash investing and financing activities:
Property and equipment purchased with capital lease		109
Transfer of systems from property and equipment into inventory	54	47
Property and equipment costs incurred but not paid included in other current liabilities	333	728
Intellectual property acquisition included in accrued liabilities	453
Supplemental cash flow disclosure:
Cash received for interest	75
Cash paid for interest	$ 7