| In millions, except per share items | Apr-30-22 | Apr-30-21 | Apr-30-20 | Apr-30-19 | Apr-30-18 | Apr-30-17 | Apr-30-16 | Apr-30-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Oncology services revenue | 49.1 | 41.0 | 32.1 | 27.1 | 20.2 | 15.4 | 11.2 | 8.9 |
| Oncology services revenue growth | 19.7% | 27.8% | 18.7% | 33.7% | 31.3% | 37.8% | 26.2% | -23.3% |
| Costs and operating expenses: | | | | | | | | |
| Cost of oncology services | 23.6 | 21.4 | 17.0 | | | | | |
| Research and development | 9.4 | 7.2 | 5.9 | 4.8 | 4.4 | 4.3 | 4.2 | 4.8 |
| Sales and marketing | 6.4 | 5.5 | 4.2 | 3.1 | 2.6 | 3.3 | 3.4 | 4.3 |
| General and administrative | 9.1 | 6.5 | 6.6 | 4.7 | 4.1 | 5.0 | 5.2 | 5.3 |
| Total costs and operating expenses | 48.5 | 40.7 | 34.0 | 26.8 | 21.6 | 22.2 | 21.5 | 22.1 |
| Income (loss) from operations | 0.6 | 0.4 | -1.9 | 0.3 | -1.4 | -6.8 | -10.3 | -13.2 |
| Operating margin | 1.2% | 0.9% | -6.0% | 1.0% | -6.7% | -44.2% | -92.3% | -149.4% |
| Other income (loss) | 0.0 | 0.1 | 0.0 | 0.0 | -0.1 | -0.1 | 0.0 | -0.2 |
| Income (loss) before provision for income taxes | 0.6 | 0.4 | -2.0 | 0.2 | -1.4 | -6.9 | -10.4 | -13.0 |
| Provision for income taxes | 0.0 | 0.1 | 0.1 | 0.1 | 0.0 | 0.0 | 0.1 | 0.1 |
| Net income (loss) | 0.5 | 0.4 | -2.1 | 0.1 | -1.5 | -6.9 | -10.4 | -13.1 |
| |
| Net income (loss) per common share outstanding | | | | | | | | |
| Net (income) loss per common share outstanding, basic (in dollars per share) | $0.04 | $0.03 | ($0.18) | $0.01 | ($0.13) | ($0.64) | ($1.20) | ($2.20) |
| Net (income) loss per common share outstanding, diluted (in dollars per share) | $0.04 | $0.02 | ($0.18) | $0.01 | ($0.13) | ($0.64) | ($10,400,000.00) | ($2.20) |
| |
| Weighted average common shares outstanding | | | | | | | | |
| Weighted average common shares outstanding, basic (in shares) | 13.2 | 13.1 | 11.8 | 11.3 | 11.0 | 10.7 | 8.7 | 6.0 |
| Weighted average common shares outstanding, diluted (in shares) | 14.2 | 14.6 | 11.8 | 14.1 | 11.0 | 10.7 | 8.7 | 6.4 |
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| Revenue, Product and Service [Extensible List] | | | | | | | | |
| Cost, Product and Service [Extensible List] | | | | | | | | |