[Investigation of the influence of metal markers on dose distributions and dose evaluation indices in intensity modulated radiation therapy plans for prostate cancer]

The aim of this study was to evaluate the influence of metal markers on dose distributions and dose evaluation indices in intensity modulated radiation therapy (IMRT) plans for prostate cancer. The dose distribution calculation in the prostate IMRT was performed in a virtual phantom with and without insertion of the metal markers. The deviations of Dmax, Dmin, homogeneity index (HI), Dmean, D2, D98, and D95 of clinical target volume (CTV) and planning target volume (PTV) were obtained for estimation of the influence on the dose evaluation indices. Analytical anisotropic algorithm (AAA) and Acuros external beam (AXB) algorithms were employed for calculating the dose distributions. There were no deviations in any dose evaluation indices in dose distributions calculated by using AAA, whereas the maximum deviations for CTV and PTV by using AXB were +7.93% and +6.43% for Dmax, -16.61% and -1.77% for Dmin, +29.46% and +8.34% for HI, +0.15% and +0.02% for Dmean, +1.50% and +0.24% for D2, respectively. Additional data were -0.20% in D98 (CTV) and -0.27% in D95 (PTV). This study suggests that local dose changes, which were produced around metal markers, affected dose distributions and the dose evaluation indices.