10. SALE OF RESEARCH AND DEVELOPMENT ASSETS (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Operating expenses:
Selling, general and administrative	$ 4,824,000	$ 4,365,000	$ 12,273,000	$ 13,602,000
Loss from discontinued operations	2,076,000	6,205,000	10,404,000	22,603,000
Discontinued Operations [Member]
Operating expenses:
Research and development	374,000	5,912,000	7,590,000	21,347,000
Selling, general and administrative	1,315,000	293,000	2,097,000	1,256,000
Restructuring charges	0	0	330,000	0
Total operating expenses	1,689,000	6,205,000	10,017,000	22,603,000
Other expense	387,000	0	387,000	0
Loss from discontinued operations	$ 2,076,000	$ 6,205,000	$ 10,404,000	$ 22,603,000