Condensed Consolidated Statement of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Apr. 30, 2017	$ 31,327	$ 10	$ 89,815	$ (55,855)	$ (2,643)
Balance, shares at Apr. 30, 2017		9,713,042
Stock-based compensation expense	221		221
Net loss	(4,928)			(4,928)
Foreign currency translation	115				115
Balance at Jul. 31, 2017	26,735	$ 10	90,036	(60,783)	(2,528)
Balance, shares at Jul. 31, 2017		9,713,042
Balance at Apr. 30, 2017	31,327	$ 10	89,815	(55,855)	(2,643)
Balance, shares at Apr. 30, 2017		9,713,042
Net loss	(9,914)
Foreign currency translation	72
Balance at Oct. 31, 2017	31,079	$ 11	99,408	(65,769)	(2,571)
Balance, shares at Oct. 31, 2017		10,783,631
Balance at Jul. 31, 2017	26,735	$ 10	90,036	(60,783)	(2,528)
Balance, shares at Jul. 31, 2017		9,713,042
Issuance of common stock from public offerings, net of issuance costs\Issuance of common stock	9,100	$ 1	9,099
Issuance of common stock from public offerings, net of issuance costs, shares\ Issuance of common stock, shares		1,070,589
Stock-based compensation expense	273		273
Net loss	(4,986)			(4,986)
Foreign currency translation	(43)				(43)
Balance at Oct. 31, 2017	31,079	$ 11	99,408	(65,769)	(2,571)
Balance, shares at Oct. 31, 2017		10,783,631
Balance at Apr. 30, 2018	27,253	$ 11	100,011	(71,660)	(1,109)
Balance, shares at Apr. 30, 2018		10,799,895
Cash received pursuant to common stock subscription agreement	5,000		5,000
Stock-based compensation expense	347		347
Net loss	(5,030)			(5,030)
Foreign currency translation	(1,320)				(1,320)
Balance at Jul. 31, 2018	26,250	$ 11	105,358	(76,690)	(2,429)
Balance, shares at Jul. 31, 2018		10,799,895
Balance at Apr. 30, 2018	27,253	$ 11	100,011	(71,660)	(1,109)
Balance, shares at Apr. 30, 2018		10,799,895
Net loss	(8,334)
Foreign currency translation	(1,127)
Balance at Oct. 31, 2018	106,951	$ 17	189,164	(79,994)	(2,236)
Balance, shares at Oct. 31, 2018		17,225,167
Balance at Jul. 31, 2018	26,250	$ 11	105,358	(76,690)	(2,429)
Balance, shares at Jul. 31, 2018		10,799,895
Issuance of common stock from public offerings, net of issuance costs\Issuance of common stock	82,811	$ 6	82,805
Issuance of common stock from public offerings, net of issuance costs, shares\ Issuance of common stock, shares		6,378,320
Issuance of common stock from exercise of stock options	25		25
Issuance of common stock from exercise of stock options, shares		4,452
Issuance of common stock from vesting of performance stock units, shares		42,500
Stock-based compensation expense	976		976
Net loss	(3,304)			(3,304)
Foreign currency translation	193				193
Balance at Oct. 31, 2018	$ 106,951	$ 17	$ 189,164	$ (79,994)	$ (2,236)
Balance, shares at Oct. 31, 2018		17,225,167