Supplemental computational phantoms to estimate out-of-field absorbed dose in photon radiotherapy

Kyle J. Gallagher, Jaad Tannous, Racile Nabha, Joelle Ann Feghali, Zeina Ayoub, Wassim Jalbout, Bassem Youssef, Phillip J. Taddei

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The purpose of this study was to develop a straightforward method of supplementing patient anatomy and estimating out-of-field absorbed dose for a cohort of pediatric radiotherapy patients with limited recorded anatomy. A cohort of nine children, aged 2-14 years, who received 3D conformal radiotherapy for low-grade localized brain tumors (LBTs), were randomly selected for this study. The extent of these patients' computed tomography simulation image sets were cranial only. To approximate their missing anatomy, we supplemented the LBT patients' image sets with computed tomography images of patients in a previous study with larger extents of matched sex, height, and mass and for whom contours of organs at risk for radiogenic cancer had already been delineated. Rigid fusion was performed between the LBT patients' data and that of the supplemental computational phantoms using commercial software and in-house codes. In-field dose was calculated with a clinically commissioned treatment planning system, and out-of-field dose was estimated with a previously developed analytical model that was re-fit with parameters based on new measurements for intracranial radiotherapy. Mean doses greater than 1 Gy were found in the red bone marrow, remainder, thyroid, and skin of the patients in this study. Mean organ doses between 150 mGy and 1 Gy were observed in the breast tissue of the girls and lungs of all patients. Distant organs, i.e. prostate, bladder, uterus, and colon, received mean organ doses less than 150 mGy. The mean organ doses of the younger, smaller LBT patients (0-4 years old) were a factor of 2.4 greater than those of the older, larger patients (8-12 years old). Our findings demonstrated the feasibility of a straightforward method of applying supplemental computational phantoms and dose-calculation models to estimate absorbed dose for a set of children of various ages who received radiotherapy and for whom anatomies were largely missing in their original computed tomography simulations.

Original languageEnglish (US)
Article number025021
JournalPhysics in Medicine and Biology
Volume63
Issue number2
DOIs
StatePublished - Jan 2018

Keywords

  • analytical model
  • computational phantoms
  • out-of-field dose
  • pediatric intracranial tumors
  • photon radiotherapy
  • stray radiation

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

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