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Updated: Aug 21, 2026
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Published on: May 8, 2018
Determination of optimum planning target volume margins for various tumor sites using electronic portal imaging
M Nalca Andrieu1, B Dirican, A Y Ozturk
1Department of Radiation Oncology, Ankara University Medical School, Ankara, Turkey. mnalca@medicine.ankara.edu.tr.
Objective:
The aim of this study is to evaluate the efficacy of electronic portal imaging (EPI) to measure the set-up errors for four different sites of irradiation caused by patient positioning.
Methods:
A total number of 95 portal images of 11 patients (3 pelvic, 1 total cranium, 3 mantle and 4 tangential fields for breast) were collected during the course of study. The first portal images after a correction of set-up errors according to the simulation films were accepted as the reference images for the subsequent sessions. By matching each portal image with the reference image, the deviations in lateral (x) and superior-inferior (y) axis for all and additionally in antero-posterior (z) axis for pelvis, and standard deviations were calculated.
Results:
The set-up errors caused by patient's positioning are completely abolished in 15 mm planning target volume (PTV) margins for all studied cases.
Conclusion:
Standard PTV margins usually completely cover the set-up errors caused by patient's positioning.
