8. SHARE-BASED COMPENSATION (Details) (USD $)	3 Months Ended		6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Share based compensation	$ 1,720,000	$ 629,000	$ 3,313,000	$ 1,291,000
Stock options
Share based compensation	1,506,000	584,000	3,009,000	1,199,000
Restricted Stock
Share based compensation	139,000	0	139,000	0
Employee Stock Purchase Plan
Share based compensation	75,000	45,000	165,000	92,000
Cost of contract manufacturing
Share based compensation	16,000	9,000	40,000	18,000
Research and development
Share based compensation	721,000	289,000	1,462,000	612,000
Selling, general and administrative
Share based compensation	$ 983,000	$ 331,000	$ 1,811,000	$ 661,000