4. STOCKHOLDERS' EQUITY (Details Narrative) - USD ($)	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Series E preferred stock issued for cash, value		$ 1,634,000	$ 60,000
August 2015 AMI Sales Agreement [Member[
Aggregate gross proceeds available in offering	$ 30,000,000
Equity Distribution Agreement [Member]
Aggregate gross proceeds available in offering			$ 20,000,000
Common Stock Purchase Agreement [Member]
Number of common stock shares issued, shares		2,645,503
Gross proceeds from the sale of common stock		$ 20,000,000
Issuance costs		$ 1,000
Common Stock
Number of common stock shares issued, shares	11,345,704	9,887,726	6,053,175
Gross proceeds from the sale of common stock	$ 27,467,000	$ 31,277,000	$ 45,872,000
Issuance costs	1,780,000	827,000	677,000
Common Stock | June 2014 AMI Agreement
Aggregate gross proceeds available in offering		25,000,000
Series E Preferred Stock [Member]
Issuance costs	$ 0	$ 58,000	$ 1,000
Series E preferred stock issued for cash, shares		70,320	2,676