CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Previously Reported	Revision of Prior Period, Adjustment	Common Stock	Common Stock Previously Reported	Treasury Stock	Additional Paid-in Capital	Additional Paid-in Capital Previously Reported	Accumulated Deficit	Accumulated Deficit Previously Reported	Accumulated Deficit Revision of Prior Period, Adjustment
Balance (in shares) at Apr. 30, 2019				11,619,538	11,619,538	0
Balance at Apr. 30, 2019	$ 2,137	$ 2,238	$ (101)	$ 12	$ 12		$ 72,924	$ 72,924	$ (70,799)	$ (70,698)	$ (101)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	600						600
Issuance of common stock on exercise of stock options and warrants (in shares)				1,107,190
Issuance of common stock on exercise of stock options	4,455			$ 1			4,454
Net income (loss)	(2,093)	(1,975)	(118)						(2,093)
Balance (in shares) at Apr. 30, 2020				12,726,728		0
Balance at Apr. 30, 2020	5,099	5,318	(219)	$ 13		$ 0	77,978		(72,892)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,035	816	219
Balance at Jan. 31, 2021	8,086	7,867	219
Balance (in shares) at Apr. 30, 2020				12,726,728		0
Balance at Apr. 30, 2020	5,099	$ 5,318	$ (219)	$ 13		$ 0	77,978		(72,892)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	598						598
Issuance of common stock on exercise of stock options and warrants (in shares)				687,338
Issuance of common stock on exercise of stock options	1,369						1,369
Net income (loss)	362								362
Balance (in shares) at Apr. 30, 2021				13,414,066		0
Balance at Apr. 30, 2021	$ 7,428			$ 13		$ 0	$ 79,945		$ (72,530)