Property and Equipment Net (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Leasehold improvements	$ 5,598	$ 5,598
Machinery and equipment	1,594	1,682
Demonstration equipment	24	24
Office furniture	644	636
Computer equipment	550	525
Computer software	1,062	1,062
Construction-in-progress	55	38
Total property and equipment, gross	10,020	10,067
Accumulated depreciation and amortization	(8,322)	(8,035)
Total property and equipment, net	1,698	2,032
Consigned Equipment
Property, Plant and Equipment [Line Items]
Demonstration equipment	$ 493	$ 502