[Is volumetric modulated arctherapy the final evolution of conformal radiotherapy?]

Relationships between various indices of doses distribution homogeneity

AIM

In this study we compared three different methods of evaluation of dose distribution.

BACKGROUND

The aim of treatment planning is to prepare the treatment plan which the criteria are defined according to the international recommendations.

MATERIALS AND METHODS

For three groups of patients, for lung, breast and prostate, treated radically in Brzozow with external beams the treatment plans were prepared. For each patient the metrics of dose distribution in the PTV defined according to the ICRU Reports 50, 83 and according to the Nordic Association of Clinical were calculated. Also Homogeneity Index defined by Yoon was used in this work. Additionally for similar group of patients treated in Warsaw the same calculations were performed. Correlations between the standard deviations and: (1) the differences between the maximum and minimum doses, and (2) the differences between near maximum and near minimum doses normalized to median dose and (3) to prescribed dose were calculated.

RESULTS

There was a very strong correlation between the standard deviation and the difference between the near-maximum and near-minimum doses for all locations regardless the prescription. Also good correlation was observed for the standard deviation and the difference between the maximum and minimum doses for patients treated in Brzozow.

CONCLUSIONS

The standard deviation may be estimated by the Homogeneity Index, however the relationship should be established for each location and each center separately.