Comparación de dosis absorbida en agua y dosis absorbida en medio en tratamientos de próstata y cabeza y cuello. Análisis con diferentes tamaños de rejilla y curvas de calibración CT

David García Riñón; Carlos Ferrer Gracia; Concepción  Huertas Martínez; Raúl  Sánchez López; Moisés  Sáez Beltrán

doi:10.37004/sefm/2022.23.1.001

Authors

David García Riñón Servicio de Radiofísica y Radioprotección, Hospital Universitario la Paz. https://orcid.org/0000-0002-6504-4894
Carlos Ferrer Gracia Servicio de Radiofísica y Radioprotección, Hospital Universitario la Paz.
Concepción Huertas Martínez Servicio de Radiofísica y Radioprotección, Hospital Universitario la Paz.
Raúl Sánchez López Servicio de Radiofísica y Radioprotección, Hospital Universitario la Paz.
Moisés Sáez Beltrán Servicio de Radiofísica y Radioprotección, Hospital Universitario la Paz.

DOI:

https://doi.org/10.37004/sefm/2022.23.1.001

Keywords:

Monte Carlo, TPS Monaco, Interface, Absorber dose to medium, Absorber dose to water

Abstract

Differences between the dose distributions calculated with D_w,m y D_m,m on the Monaco planner for treatments of prostate and neck and head are analyzed. A division of organs in the form of layers of different thicknesses is performed to evaluate the influence of the calculation grid size (3mm and 1mm). Study of how affect the curve of calibration CT to calculated doses is made. The results show a variation, (D_w,m - D_m,m)/D_w,m, mean doses of 0.1%-0.3% on rectum and bladder, around 1% on spinal cord and oral cavity, 3% on femoral heads and 7% on jawbone. The coverage of PTV is superior in D_w,m in a 0.04%, 1.22% for prostate and 0.92%, 5.8% in head and neck (V95%, V100% respectively). Differences in head and neck regarding coverage of PTV, according his grade of overlap with bone, are important enough for the choice of absorption medium to affect tumour control. Dose variations between regions of different densities are superior with 1mm size grid, showing a higher sensibility to the interface. The variation with the CT calibration curve is only appreciable (0.38%) in organs with a density very different from that of water.

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