The Comparative Analysis of External Dose Reconstruction in EPID and Internal Dose Measurement Using Monte Carlo Simulation

Joo-Young Jung; Do-Kun Yoon; Tae-Suk Suh

doi:10.14316/pmp.2013.24.4.253

Journal List > Prog Med Phys > v.24(4) > 1098397

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Jung, Yoon, and Suh: The Comparative Analysis of External Dose Reconstruction in EPID and Internal Dose Measurement Using Monte Carlo Simulation

Original Article

Progress in Medical Physics 2013;24(4):253-258.

Published online: 17 December 2013

DOI: https://doi.org/10.14316/pmp.2013.24.4.253

The Comparative Analysis of External Dose Reconstruction in EPID and Internal Dose Measurement Using Monte Carlo Simulation

Joo-Young Jung, Do-Kun Yoon, Tae-Suk Suh

Department of Biomedical Engineering, Research Institute of Biomedical Engineering, School of Medicine, The Catholic University of Korea, Seoul, Korea

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The purpose of this study is to evaluate and analyze the relationship between the external radiation dose reconstruction which is transmitted from the patient who receives radiation treatment through electronic portal imaging device (EPID) and the internal dose derived from the Monte Carlo simulation. As a comparative analysis of the two cases, it is performed to provide a basic indicator for similar studies. The geometric information of the experiment and that of the radiation source were entered into Monte Carlo n-particle (MCNPX) which is the computer simulation tool and to derive the EPID images, a tally card in MCNPX was used for visualizing and the imaging of the dose information. We set to source to surface distance (SSD) 100 cm for internal measurement and EPID. And the water phantom was set to be 100 cm of the source to surface distance (SSD) for the internal measurement and EPID was set to 90 cm of SSD which is 10 cm below. The internal dose was collected from the water phantom by using mesh tally function in MCNPX, accumulated dose data was acquired by four-portal beam exposures. At the same time, after getting the dose which had been passed through water phantom, dose reconstruction was performed using back-projection method. In order to analyze about two cases, we compared the penetrated dose by calibration of itself with the absorbed one. We also evaluated the reconstructed dose using EPID and partially accumulated (overlapped) dose in water phantom by four-portal beam exposures. The sum dose data of two cases were calculated as each 3.4580 MeV/g (absorbed dose in water) and 3.4354 MeV/g (EPID reconstruction). The result of sum dose match from two cases shows good agreement with 0.6536% dose error.

Keywords: MCNPX, Monte Carlo simulation, EPID dose-reconstruction, Internal dose measurement, Calibration

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Fig. 1.

The scheme of this study. The absorbed dose data both Water phantom and EPID were acquired from four-portal exposure.

Fig. 2.

Percent depth dose (PDD) the voxel with water phantom (24.2×24.2×24.2 cm³) using 2 MeV photon source. Region of interesting set 8-16, equation of this section was adapted for calibration.

Fig. 3.

Lateral dose profile from EPID (without phantom; lower line, with phantom; upper line) [m1]. This figure is calibration data by calculation absorbed dose factor and EPID extraction dose factor.

Fig. 4.

Accumulated dose diagram of four-portal beam exposures. (a) absorbed dose of water phantom (b) dose reconstruction diagram of EPID dose with calculation factor using back-projection.

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