Summary of Significant Accounting Policies - Reconciliation of the numerator and denominator used in computing basic and diluted net loss per share (Details) (USD $)	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Summary Of Significant Accounting Policies - Reconciliation Of Numerator And Denominator Used In Computing Basic And Diluted Net Loss Per Share Details
Loss (numerator)	$ (781,663)	$ (4,182,611)	$ (3,005,137)	$ (6,215,443)
Shares (denominator)	1,782,925	1,783,885	1,784,898	1,766,735
Net loss per share, basic	$ (0.44)	$ (2.34)	$ (1.68)	$ (3.52)
Loss (numerator)	$ (781,663)	$ (4,182,611)	$ (3,005,137)	$ (6,215,443)
Shares (denominator)	1,782,925	1,783,885	1,784,898	1,766,735
Net loss per share, diluted	$ (0.44)	$ (2.34)	$ (1.68)	$ (3.52)