CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	6 Months Ended
	Oct. 31, 2012	Oct. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (16,417,000)	$ (20,147,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	1,291,000	1,679,000
Depreciation and amortization	526,000	426,000
Amortization of discount on notes payable and debt issuance costs	0	32,000
Loss on early extinguishment of debt	1,696,000	0
Changes in operating assets and liabilities:
Trade and other receivables, net	33,000	291,000
Inventories, net	(1,815,000)	2,106,000
Prepaid expenses and other current assets, net	(90,000)	(171,000)
Other non-current assets	0	747,000
Accounts payable	(316,000)	307,000
Accrued clinical trial site and related fees	(553,000)	(70,000)
Accrued payroll and related expenses	(74,000)	68,000
Deferred revenue	2,414,000	(3,636,000)
Customer deposits	3,635,000	(56,000)
Other current liabilities	70,000	(35,000)
Other long-term liabilities	(58,000)	(193,000)
Net cash used in operating activities	(9,658,000)	(18,652,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property acquisitions	(309,000)	(685,000)
Increase in other assets	(201,000)	(192,000)
Net cash used in investing activities	(510,000)	(877,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance costs of $620,000 and $785,000, respectively	17,595,000	15,450,000
Proceeds from issuance of notes payable, net of issuance costs of $251,000	14,749,000	0
Proceeds from exercise of stock options and under Employee Stock Purchase Plan	248,000	96,000
Principal payments on notes payable	(15,000,000)	(1,000,000)
Payment of final fee on notes payable	(975,000)	0
Principal payments on capital leases	(39,000)	(37,000)
Net cash provided by financing activities	16,578,000	14,509,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	6,410,000	(5,020,000)
CASH AND CASH EQUIVALENTS, beginning of period	18,033,000	23,075,000
CASH AND CASH EQUIVALENTS, end of period	24,443,000	18,055,000
SCHEDULE OF NON-CASH INVESTING AND FINANCING ACTIVITIES:
Accounts payable for purchase of property	0	72,000
Fair market value of warrants issued in connection with notes payable	$ 470,000	$ 0