Does CTV-PTV margin have an impact on estimation of cumulated dose distribution?
Warsaw Medical Physics Meeting 2015
The purpose of this work was to test whether the CTV-PTV margin has an impact on estimation of cumulated dose distribution (CDDall). For patients with prostate cancer treated in our clinic set-up errors were recorded. For each patient treatment plans in three techniques were prepared: 3D-CRT, IMRT and VMAT. We prepared plans for different CTV-PTV margin: 0, 0.2, 0.4, 0.6, 0.8, 1.0 cm. For each treatment plan and each fraction the dose distribution was calculated with the isocenter corrected for the set-up error. CDDall was calculated as the sum of all dose distributions for each single fraction. Estimated Dose Distribution EDDn was calculated with bootstrap methodology. EDDn and CDDall were compared using homemade Python program. The 3D gamma concept with 2mm and 2% of max dose was used for comparison of each pair of dose distributions. Results showed that we can use the same number of fractions to estimate cumulated dose distribution for different margins.
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