Open AccessEvaluation of target dose based on water-equivalent thickness in external beam radiotherapy
Author(s) -
Behnaz Ghanbar Moghaddam,
Masoud Vahabi-Moghaddam,
Alireza Sadremomtaz
Publication year - 2013
Publication title -
journal of medical physics/journal of medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.292
H-Index - 24
eISSN - 1998-3913
pISSN - 0971-6203
DOI - 10.4103/0971-6203.106605
Subject(s) - dosimeter , nuclear medicine , dosimetry , thermoluminescent dosimeter , thorax (insect anatomy) , percentage depth dose curve , radiation therapy , beam (structure) , medicine , dose profile , thermoluminescent dosimetry , radiation treatment planning , materials science , radiology , ionization chamber , optics , physics , anatomy , ion , quantum mechanics , ionization
In vivo dosimetry was carried out for 152 patients receiving external beam radiotherapy and the treatment sites were divided into two main groups: Thorax, Abdomen, and Pelvic (120 fields) and Head and Neck (52 fields). Combined entrance and exit dose measurements were performed using LiF: Mg, Cu, P thermoluminescent dosimeters (TLDs). Water-equivalent (effective) thicknesses and target dose were evaluated using dose transmission data. The ratio of measured to expected value for each quantity was considered as an indicator for the accuracy of the parameter. The average ratio of the entrance dose was evaluated as 1.01 ± 0.07. In the diameter measurement, the mean ratio of effective depth divided by the contour depth is 1.00 ± 0.13 that shows a wide distribution which reflects the influence of contour inaccuracies as well as tissue inhomogeneities. At the target level, the mean ratio of measured to the prescribed dose is 1.00 ± 0.07. According to our findings, the difference between effective depth and patient depth has a direct relation to target dose discrepancies. There are some inevitable sources which may cause the difference. Evaluation and application of effective diameter in treatment calculations would lead to a more reliable target dose, especially for fields which involve Thorax, Abdomen, and Pelvic.