CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (24,833,000)	$ (22,887,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	1,206,000	2,591,000
Depreciation and amortization	1,945,000	1,850,000
Loss on disposal of property and equipment	401,000	0
Changes in operating assets and liabilities:
Trade and other receivables	(225,000)	(3,024,000)
Inventories	18,881,000	(17,643,000)
Prepaid expenses	554,000	(396,000)
Other non-current assets	9,000	233,000
Accounts payable	(3,895,000)	(1,153,000)
Accrued clinical trial and related fees	945,000	(4,467,000)
Accrued payroll and related expenses	(2,208,000)	(184,000)
Deferred revenue	(21,867,000)	16,337,000
Customer deposits	585,000	1,998,000
Other accrued expenses and current liabilities	(64,000)	(801,000)
Deferred rent, less current portion	465,000	(70,000)
Net cash used in operating activities	(28,101,000)	(27,616,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property and equipment acquisitions	(2,129,000)	(2,644,000)
(Increase) decrease in other assets	(15,000)	205,000
Net cash used in investing activities	(2,144,000)	(2,439,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance costs of $111,000 and $340,000, respectively	4,193,000	11,604,000
Proceeds from issuance of Series E preferred stock, net of issuance costs of nil and $58,000, respectively	0	1,576,000
Proceeds from issuance of common stock under Employee Stock Purchase Plan	217,000	254,000
Proceeds from exercise of stock options	398,000	0
Dividends paid on Series E preferred stock	(3,244,000)	(3,198,000)
Principal payments on capital lease	(180,000)	(65,000)
Net cash provided by financing activities	1,384,000	10,171,000
NET DECREASE IN CASH AND CASH EQUIVALENTS	(28,861,000)	(19,884,000)
CASH AND CASH EQUIVALENTS, beginning of period	46,799,000	61,412,000
CASH AND CASH EQUIVALENTS, end of period	17,938,000	41,528,000
SCHEDULE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accounts payable for purchase of property and equipment	27,000	420,000
Property and equipment acquired under capital lease	$ 0	$ 319,000