Quality assurance of radiotherapy in the ongoing EORTC 22042–26042 trial for atypical and malignant meningioma: results from the dummy runs and prospective individual case Reviews

Table 2 Quantitative parameters measuring quality: definition of indices

Parameter [ref]	Definition	Optimal Value	Acceptable	Minor Violation	Major Violation
RTOG Conformity Index (CI) [11]	V _pi / V _T	1.0	1.0 – 2.0	≥ 0.9-1.0 or > 2.0-2.5	< 0.9 or >2.5
Target Coverage (TC) [12]	V _T,pi / V _T	1.0	≥0.95 – 1.0	0.90 - 0.95	< 0.90
Homogeneity Index (HI)* [13]	(D ₂ %- D ₉₈ %) / D ₅₀ %	0.0	0.0 - 0.12	0.12 - 0.2	> 0.2

*HI minor and major deviations defined according to protocol deviation parameters for dose conformity and PTV D ₂ %.
Abbreviations: V_pi, Prescription Isodose Volume; V_T, Volume Target; V_T,pi, 95% isodose volume within the target; D₂%, D₅₀%, D₉₈%, Dose received by 2, 50 and 98 percent of the PTV, respectively.

ISSN: 1748-717X