CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (15,390,000)	$ (16,417,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	3,313,000	1,291,000
Depreciation and amortization	493,000	526,000
Loss on early extinguishment of debt	0	1,696,000
Changes in operating assets and liabilities:
Trade and other receivables, net	(274,000)	33,000
Inventories	306,000	(1,815,000)
Prepaid expenses and other current assets, net	(165,000)	(90,000)
Accounts payable	(527,000)	(316,000)
Accrued clinical trial and related fees	99,000	(553,000)
Accrued payroll and related expenses	(430,000)	(74,000)
Deferred revenue	(703,000)	2,414,000
Customer deposits	(401,000)	3,635,000
Other accrued expenses and current liabilities	115,000	70,000
Other long-term liabilities	(46,000)	(58,000)
Net cash used in operating activities	(13,610,000)	(9,658,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property and equipment acquisitions	(53,000)	(309,000)
Increase in other assets	(1,040,000)	(201,000)
Net cash used in investing activities	(1,093,000)	(510,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance costs of $722,000 and $620,000, respectively	23,555,000	17,595,000
Proceeds from issuance of notes payable, net of issuance costs of $251,000	0	14,749,000
Proceeds from issuance of common stock under Employee Stock Purchase Plan	282,000	214,000
Proceeds from exercise of stock options	129,000	34,000
Principal payments on notes payable	0	(15,000,000)
Payment of final fee on notes payable	0	(975,000)
Principal payments on capital leases	(24,000)	(39,000)
Net cash provided by financing activities	23,942,000	16,578,000
NET INCREASE IN CASH AND CASH EQUIVALENTS	9,239,000	6,410,000
CASH AND CASH EQUIVALENTS, beginning of period	35,204,000	18,033,000
CASH AND CASH EQUIVALENTS, end of period	44,443,000	24,443,000
SCHEDULE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accounts payable for purchase of property	77,000	0
Fair market value of warrants issued in connection with notes payable	$ 0	$ 470,000