Table 3. Spearman's rank correlation coefficients for the average tissue depth and other parameters.
| Parameters | rho | p-value |
| PTV coverage (%) by 80% IDS | 0.156 | 0.189 |
| PTV coverage (%) by 90% IDS | 0.167 | 0.159 |
| PTV D99 (%) | 0.204 | 0.083 |
| PTV D95 (%) | 0.224 | 0.057 |
| CTV coverage (%) by 90% IDS | 0.488 | <0.001 |
| CTV D99 (%) | 0.711 | <0.001 |
| CTV D95 (%) | 0.700 | <0.001 |
| Dmax (%) | −0.492 | <0.001 |
| HI (Dmax/D99) | −0.482 | <0.001 |
| PITV (80% IDS) | 0.115 | 0.334 |
| PITV (D99) | −0.212 | 0.072 |
| PITV (D95) | −0.365 | 0.001 |
CTV, clinical target volume; Dmax, maximum dose; HI (Dmax/D99), homogeneity index defined as the ratio of Dmax to D99; IDS, isodose surface; PITV, ratio of prescription isodose volume/target volume; PTV, planning target volume.
Significant results are shown in bold.