Table 12. Correlations between GTV and irradiated isodose volumes in BED-based dose prescriptions to GTV DV-0.01 cc and the GTV thresholds at which the risk of brain radionecrosis increases.
*Diameters of spheres corresponding to GTVs above the IIV thresholds relevant to the risk of brain radionecrosis
The suitability of linear approximations for the correlations between the GTVs and the IIVs is shown, along with the coefficients of determination (R2)
GTV: gross tumor volume; BED: biologically effective dose; DV-0.01 cc: a minimum dose to cover a target volume minus 0.01 cc; IIV: irradiated isodose volume (including a target volume); fr: fraction(s); vol.: volume
| GTV DV-0.01 cc | IIV | Threshold vol. (Risk) | Linear approximation formula | R2 | GTV exceeding the threshold volume (Diameter*) |
| 43.0 Gy (5 fr) | 24 Gy vol. | <20.0 cc (<10%) | y = 2.2288x + 1.1373 | 0.9996 | 8.47 cc (25.3 mm) |
| 36.3 Gy (3 fr) | 20 Gy vol. | <20.0 cc (<10%) | y = 2.2659x + 1.1634 | 0.9996 | 8.32 cc (25.1 mm) |
| 23.8 Gy (1 fr) | 12 Gy vol. | 5.0 cc (10%) | y = 2.5339x + 1.4323 | 0.9996 | 1.41 cc (13.9 mm) |
| 10.0 cc (15%) | 3.39 cc (18.6 mm) |