Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2012

Stock-Based Compensation Expense

The following table presents stock-based compensation expense in the Company’s consolidated statements of operations:

	Year ended December 31, 2012		Nine Months ended December 31,				Year ended March 31, 2011
			2011		2010 (unaudited)
Cost of product revenue	$	45,000	$	35,000	$	38,000	$	48,000
Research and development		219,000		191,000		164,000		226,000
Selling, general and administrative		760,000		504,000		546,000		729,000
Total	$	1,024,000	$	730,000	$	748,000	$	1,003,000

Estimated Weighted Average Assumptions

The fair value of share-based awards granted during the year ended December 31, 2012, the nine-month fiscal year ended December 31, 2011, the nine-month period ended December 31, 2010 and the fiscal year ended March 31, 2011 were calculated using the following estimated assumptions:

	Year ended December 31,	Nine Months ended December 31,		Years ended March 31,
	2012	2011	2010	2011
Expected term (years)	6.5	6.5	6.5	6.5
Volatility	49.76% - 53.54%	53.09% - 55.76%	57.58% - 63.60%	55.94% - 63.60%
Risk-free interest rate	0.89% - 1.06%	1.25% - 2.38%	1.81% - 2.62%	1.81% - 2.83%
Expected dividend yield	—	—	—	—

Summary of Option Activity

Information regarding option activity for the year ended December 31, 2012 under the Plans is summarized below:

	Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Options outstanding at December 31, 2011		2,823,400		$	4.05
Granted		368,690			3.65
Exercised		(609,400	)		3.06
Forfeited/cancelled		(267,600	)		4.44
Options outstanding at December 31, 2012		2,315,090		$	4.20		6.16	$	4,854,412
Options exercisable at December 31, 2012		1,447,600		$	4.39		4.96	$	2,783,183
Vested and expected to vest at December 31, 2012 (1)		2,186,609		$	4.21		6.05	$	4,570,615

(1) This represents the number of vested options as of December 31, 2012 plus the number of unvested options expected to vest as of December 31, 2012 based on the unvested outstanding options at December 31, 2012 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.