Commitment and Contingencies (Details) - USD ($)	3 Months Ended
	Jul. 31, 2022	Jul. 31, 2021
Commitments and Contingencies [Line Items]
Royalty expense	$ 76,000	$ 44,000
Minimum
Commitments and Contingencies [Line Items]
Royalty fee per tumor sample	$ 0
Royalty payment, as percent of contract price	2.00%
Maximum
Commitments and Contingencies [Line Items]
Royalty fee per tumor sample	$ 30,000
Royalty payment, as percent of contract price	20.00%