Evaluation of Organs at Risk’s Dose in External Radiotherapy of Brain Tumors

AUTHORS

Hamideh Nazemi-Gelyan 1 , Hadi Hasanzadeh 1 , * , Yasha Makhdumi 2 , Sara Abdollahi 3 , Fatemeh Akbari 2 , Fatemeh Varshoee-Tabrizi 2 , Hamzeh Almasrou 2 , Alireza Nikoofar 3 , Mostafa RezaeiTavirani 4

1 Dept. of Medical Physics, Semnan University of Medical Sciences, Semnan, Iran

2 Reza Radiotherapy Oncology Charity Center, Mashhad, Iran

3 Dept. of Radiotherapy, Iran University of Medical Sciences, Tehran, Iran

4 Proteomics Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran

How to Cite: Nazemi-Gelyan H, Hasanzadeh H, Makhdumi Y, Abdollahi S, Akbari F, et al. Evaluation of Organs at Risk’s Dose in External Radiotherapy of Brain Tumors, Int J Cancer Manag. 2015 ; 8(1):e80583.

ARTICLE INFORMATION

International Journal of Cancer Management: 8 (1); e80583
Published Online: February 28, 2015
Article Type: Research Article
Received: October 25, 2014
Accepted: December 14, 2014

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Abstract

Background: Radiotherapy plays an important role in the management of most malignant and many benign primary central nervous system (CNS) tumors. Radiotherapy affects both tumor cells and uninvolved normal cells; so, it is important to estimate absorbed dose to organs at risk in this kind of treatment. The aim of this study was to determine the absorbed dose to chiasma, lens, optic nerve, retina, parotid, thyroid and submandibular gland in frontal lobe brain tumors radiotherapy based on treatment planning system (TPS) calculation and direct measurement on the phantom.

Methods: A head and neck phantom was constructed using natural human bone and combination of paraffin wax and Sodium Chloride (NaCl) as tissueequivalent material. Six cylinders were made of phantom material which had cavities to insert Thermoluminescent Dosimeters (TLDs) at several depths in order to measure absorbed dose to chiasma, lens, optic nerve, retina, parotid, thyroid and submandibular gland. Three routine conventional plans associated with tumors of this region and a new purposed technique were performed on the phantom and dose distribution and absorbed dose to critical organs were compared using treatment planning system (TPS) calculation and direct measurement on the phantom.

Results: Absorbed doses were measured with calibrated TLDs and are expressed in centigray (cGy). In all techniques absorbed dose to all organs except the lenses were at their tolerance dose levels and in the new purposed technique, absorbed dose to chiasma was significantly reduced.

Conclusion: Our findings showed differences in the range of 1-5% in all techniques between TPS calculation and direct measurements for all organs except submandibular glands and thyroid. Because submandibular glands and thyroid are far from primary radiation field, TLD reading in these regions although small but differs from TPS calculation which shows very smaller doses. This might be due to scattered radiation which is not well considered in the TPS. In the new technique, because the chiasma is out of the radiation field, absorbed dose was reduced significantly

Keywords

Brain tumor External Radiotherapy Dosimetry Phantom

© 2015, Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.

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