Sensitivity Analysis of Gamma Index Calculations for Dosimetry Audits in Advanced Radiotherapy

Gamma Indices are a widely used metric for the comparison of measured and predicted doses in dosimetry audits for advanced radiotherapy. Various steps in the measurement pipeline and analysis approach, as well as different computational models to calculate the gamma index, can introduce variability in the results. In this paper the authors investigate the sensitivity of gamma index measurements to changes in the factors in the dosimetry audit pipeline using the in house developed Versatile Independent Gamma Analysis sOftware (VIGO). Our results indicate that the choice of calibrated size and shape for the region of interest introduce the most variability in the measurement. Standardising these factors can help reduce overall variability in the measurement results, and therefore the radiation received by a patient, improving the accuracy and efficiency of radiotherapy.