Table 1.
Mathematical definition of plan quality metrics studied
| Dosimetric index | Definition | Reference |
| Coverage | Quality of coverage = Imin/RI | RTOG8 |
| Coverage, % = (TVPIV/TV) × 100 | ICRU 628, 9 | |
| Homogeneity | HIRTOG = Imax/RI | RTOG8 |
| HIICRU= (D2%–D98%)/D50% | ICRU 8310 | |
| CIRTOG = PIV/TVCN = (TVRI/TV) × (TVRI/VRI) | RTOG8Van’t Riet et al11 | |
| CIPaddick = (TVPIV2/TV × PIV) | Paddick12, ICRU 9114 | |
| Conformity indices | CIgeometric (g) = LUF + HTOF | SALT8 |
| CGIc = 100 × TV/PIV | Wagner et al15 | |
| CI= (TVPIV/PIV) | Lomax and Scheib16 | |
| R50% = (PIV50%PIV)/PTV | RTOG 0915 | |
| Gradient | Gradient index = (PIV50%PIV /PIV) | Paddick and Lippitz17 |
| Gradient (cm) = (Reff,50%RX –Reff,RX) | Wagner et al15 | |
| Gradienteff = 50 %/(Reff,50%RX –Reff,RX) | Mayo et al18 |
CI, conformity index; CN, confirmation number; Dx%, minimal dose to the x% highest irradiated target volume; gradienteff, effective gradient. (Note: in our study, Prescription isodose = reference isodose = 100%); HI, homogeneity index; HTOF, healthy tissue overdosage factor (HTVRI/TV); HTVRI, healthy tissue volume covered by the reference isodose; Imax, maximum isodose in the target; Imin, minimal isodose surrounding the target; LUF, lesion underdosage factor (TV<RI/TV); PIV, prescription isodose volume; PTV, planning target volume; Reff, RX, Reff, 50%RX = effective radii of 100 and 50% isodoses (Reff); RI, reference isodose; TV<RI = target volume receiving less than reference dose; VRI, volume of reference isodose .