CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (4,215)	$ (21,813)	$ (28,159)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,746	2,562	2,463
Stock-based compensation	1,595	1,538	3,363
Loss on disposal of assets	127	1,692	1
Gain on sale of research and development assets	(1,000)	(8,000)	0
Changes in operating assets and liabilities:
Accounts receivable	(3,620)	3,988	(4,883)
Contract asssets	(1,439)	0	0
Inventories	1,701	16,970	(16,913)
Prepaid expenses and other assets	(28)	153	434
Accounts payable	2,125	(1,271)	(3,804)
Accrued payroll and related costs	976	(2,491)	372
Contract liabilities	(5,371)	(17,582)	11,275
Other accrued expenses and current liabilities	(642)	1,009	(407)
Assets and liabilities of discontinued operations	(4,550)	(2,747)	(2,911)
Net cash used in operating activities	(11,595)	(25,992)	(39,169)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(1,502)	(3,793)	(3,627)
Decrease in other assets	0	0	568
Proceeds from sale of property and equipment	46	0	0
Proceeds from sale of research and development assets	6,000	3,000	0
Net cash provided by (used in) investing activities	4,544	(793)	(3,059)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance costs	0	25,687	30,450
Proceeds from issuance of preferred stock, net of issuance costs	0	0	1,576
Proceeds from issuance of common stock under employee stock purchase plan	258	317	526
Proceeds from exercise of stock options	1,278	752	31
Dividends paid on preferred stock	(4,325)	(4,325)	(4,279)
Principal payments on capital leases	(74)	(180)	(139)
Net cash (used in) provided by financing activities	(2,863)	22,251	28,165
Change in cash, cash equivalents and restricted cash	(9,914)	(4,534)	(14,063)
Cash, cash equivalents and restricted cash, beginning of period	43,415	47,949	62,012
Cash, cash equivalents and restricted cash, end of period	33,501	43,415	47,949
SUPPLEMENTAL INFORMATION:
Interest paid	11	4	6
SCHEDULE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Unpaid purchases of property and equipment	318	180	658
Property and equipment acquired under capital lease	245	0	319
Receivable related to the sale of research and development assets	$ 0	$ 5,000	$ 0