Stockholders' Equity (Summary of Stock Option Activity) (Details) (USD $)	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012		Apr. 30, 2011		Apr. 30, 2010	Apr. 30, 2013
Stock Compensation Information [Abstract]
Shares, outstanding	2,632,115	2,152,183		1,663,497
Shares, Granted	403,500	839,400		656,100
Shares, Exercised		(124,500)		(16,000)
Shares, Canceled or expired	(1,221,016)	(234,968)		(151,414)
Shares, outstanding	1,814,599	2,632,115		2,152,183		1,663,497
Weighted average exercise price, outstanding	$ 3.18	$ 3.38		$ 3.34
Weighted average exercise price, granted	$ 1.27	$ 2.38		$ 3.38
Weighted average exercise price, exercised		$ 1.40		$ 1.28
Weighted average exercise price, canceled or expired	$ 3.07	$ 3.11		$ 3.15
Weighted average exercise price, outstanding	$ 2.83	$ 3.18		$ 3.38		$ 3.34
Weighted average remaining contractual term, outstanding	6 years 11 months 1 day	7 years 2 months 27 days		6 years 10 months 28 days		7 months 14 days
Aggregate intrinsic value, outstanding	$ 4,449	$ 550,903	[1]	$ 1,271,375	[1]		$ 15,551
Weighted average remaining contractual term, outstanding	6 years 11 months 1 day	7 years 2 months 27 days		6 years 10 months 28 days		7 months 14 days

[1] Aggregate intrinsic value is defined as the difference between the current market value and the exercise price and is estimated using the closing price of the Company’s common stock on the last trading day of the periods ended as of the dates indicated