CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Apr. 30, 2018	$ 3	$ 11	$ (1,252)	$ 72,070	$ (70,826)
Balance (in shares) at Apr. 30, 2018		11,003,228	269,685
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	636			636
Issuance of common stock for services	6			6
Issuance of common stock (in shares)		5,462
Issuance of common stock on exercise of stock options and warrants	1,465	$ 1	$ 1,252	212
Issuance of common stock on exercise of stock options and warrants (in shares)		610,848	(269,685)
Net income (loss)	128				128
Balance at Apr. 30, 2019	2,238	$ 12	$ 0	72,924	(70,698)
Balance (in shares) at Apr. 30, 2019		11,619,538	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	600			600
Issuance of common stock on exercise of stock options and warrants	4,455	$ 1		4,454
Issuance of common stock on exercise of stock options and warrants (in shares)		1,107,190
Net income (loss)	(1,975)				(1,975)
Balance at Apr. 30, 2020	$ 5,318	$ 13	$ 0	$ 77,978	$ (72,673)
Balance (in shares) at Apr. 30, 2020		12,726,728	0