Daniel Gibbor Gaspersz, Josua Timotius Manik

ANALISIS PENGARUH KETIDAKHOMOGENAN FANTOM TERHADAP DISTRIBUSI DOSIS ELEKTRON MENGGUNAKAN SIMULASI MONTE CARLO

Introduction

Analisis pengaruh ketidakhomogenan fantom terhadap distribusi dosis elektron menggunakan simulasi monte carlo. Simulasi Monte Carlo menganalisis pengaruh fantom tidak homogen terhadap distribusi dosis elektron radioterapi. Temukan perbedaan signifikan PDD, R100, & R50 dibandingkan fantom homogen.

Abstract

The usage of homogeneous phantom in the calibration of LINAC is the standard in radiotherapy. However, a homogeneous phantom cannot accurately represent the complexity of the human body. This study was conducted to perform a Monte Carlo simulation of electron beam irradiation on an inhomogeneous phantom and then compare the resulting dose distribution values, in the form of PDD, with the PDD values obtained from a homogeneous phantom. Irradiation was performed with a 6.6 MeV electron beam on an inhomogeneous phantom resembling the human body. It was discovered that there is a significant difference between the R100 and R50 values of the inhomogeneous phantom in comparison to the homogeneous water phantom. The R100 value of the inhomogeneous value differs by 53.33% compared to the homogeneous phantom, while the R50 value differs by 41.07%. This indicates the influence of electron beam interaction with the inhomogeneous phantom on the resulting dose distribution. In the PDD curve, it is observed that the electron beam passing through the inhomogeneous medium experiences a greater loss of kinetic energy compared to the homogeneous medium. It was found that there’ a significant difference between the PDD values generated in the inhomogeneous phantom compared to the homogeneous phantom.

Review

This study addresses a critically important aspect of radiotherapy dosimetry by investigating the influence of phantom inhomogeneity on electron dose distribution, a topic with direct implications for clinical practice. The authors correctly identify the inherent limitation of homogeneous phantoms in accurately representing the complex anatomical variations within the human body. Employing Monte Carlo simulations with a 6.6 MeV electron beam, the research systematically compares Percent Depth Dose (PDD) values between an inhomogeneous phantom, designed to resemble human tissue, and a standard homogeneous water phantom, focusing on key parameters like R100 and R50. The findings presented are highly significant and warrant close attention. The study reveals substantial quantitative differences, reporting a 53.33% deviation in R100 and a 41.07% deviation in R50 for the inhomogeneous phantom compared to its homogeneous counterpart. These stark differences clearly demonstrate that electron beams experience greater kinetic energy loss when traversing heterogeneous media. This empirically supported observation underscores the urgent need to integrate tissue inhomogeneity considerations into electron beam treatment planning to ensure precise dose delivery, optimize treatment outcomes, and safeguard surrounding healthy tissues. The use of Monte Carlo simulation, a gold standard for radiation transport, provides a robust methodology for these complex calculations. While the study provides compelling evidence, a more detailed description of the "inhomogeneous phantom resembling the human body," including its specific materials, densities, and anatomical structures, would enhance its reproducibility and aid in comparing results across different studies. Future research could build upon this foundation by exploring a broader spectrum of electron energies, simulating various complex anatomical regions, and potentially seeking experimental validation to corroborate these simulation results. Despite this, the paper makes a valuable contribution by quantitatively highlighting the profound impact of tissue inhomogeneity on electron dose distribution, offering crucial insights for refining and improving the accuracy and safety of electron beam radiotherapy.

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