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New calculation method for 3D dose distribution in tetrahedral-mesh phantoms in Geant4
Han, Min Cheol,Ku, Youngmo,Lee, Hyun Su,Yeom, Yeon Soo,Han, Haegin,Kim, Chan Hyeong Elsevier 2019 PHYSICA MEDICA Vol.66 No.-
<P><B>Abstract</B></P> <P>The tetrahedral-mesh (TM) geometry, which is a very promising geometry for computational human phantoms, has a limitation in 3D dose distribution calculation for medical applications. Even though Geant4 provides the read-out geometry for calculating 3D dose distribution in the TM geometry, this method significantly slows down the computation speed. In the present study, we developed a new method, called Moving Voxel-based Dose-Distribution Calculator (MVDDC), to rapidly calculate a 3D dose distribution in a TM geometry. To evaluate the performance of the MVDDC method, a simple TM cubic phantom and a human phantom were implemented in Geant4. Subsequently, the phantoms were irradiated with proton spot beams under various conditions, and the obtained results were compared with those of the read-out geometry method. The results show that there is no significant difference between the dose distributions calculated using the new method and the read-out geometry method. With respect to the computational performance, the speeds of simulations using the MVDDC were approximately 1.4–2.7 times faster than those of the simulations using the read-out geometry method.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A tetrahedral-mesh geometry is a promising geometry for dose calculation in Geant4. </LI> <LI> The conventional calculation method for TM geometry is slow. </LI> <LI> We developed a new calculation method for rapid dose calculation in TM. </LI> <LI> Regarding accuracy, there is no significant difference compared with previous. </LI> <LI> Regarding speed, the new method is 1.4–2.7 times faster than previous one. </LI> </UL> </P>
Kim, Min Chae,Kim, Hyoungtaek,Han, Haegin,Lee, Jungil,Lee, Seung Kyu,Chang, Insu,Kim, Jang-Lyul,Kim, Chan Hyeong Elsevier 2019 Radiation measurements Vol.126 No.-
<P><B>Abstract</B></P> <P>In case of a radiation emergency, thermoluminescence (TL) and optically stimulated luminescence (OSL) measurements from materials in a mobile phone have been developed to enable classification of exposed individuals within a short period of time. A reconstructed dose from a mobile phone does not, however, correspond directly to a human body dose. Therefore, several studies were tried to convert a phone dose to a human body dose. Because of the difficulty in obtaining conversion factors experimentally, Monte Carlo simulations have been carried out using human phantoms for various accident situations. In recent years phantoms made of mesh have been developed to solve some problems in traditional voxel phantoms such as limited posture. In the present study, simulations using the GEANT4 computer code were performed to obtain conversion factors using mesh phantoms. The geometry of a mobile phone was designed, reflecting latest structures, and a display glass was selected as a dosimetric material due to its wide detection area with a high radiation sensitivity. Four different positions (chest, hip, thigh, and hand) of a mobile phone on the phantom were considered. In addition, six exposure conditions of anterior-posterior (AP), posterior-anterior (PA), left-lateral (LLAT), right-lateral (RLAT), isotropic (ISO), and rotational (ROT) exposure geometries and three different postures of standing, kneeling, and squatting were selected to reflect actual working situations. Three commonly used radiation sources (Iridium-192, Cesium-137, and Cobalt-60) were applied.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Simulation was conducted to convert a phone dose to human body dose using the mesh phantoms for various postures. </LI> <LI> The evaluated doses of a mobile phone were differently affected by body shielding effects. </LI> <LI> Four different positions (chest, hip, thigh, and hand) of a mobile phone on the phantom were considered. </LI> </UL> </P>
Se Hyung Lee,Bo-Wi Cheon,Chul Hee Min,Haegin Han,Chan Hyeong Kim,Min Cheol Han,Seonghoon Kim Korean Society of Medical Physics 2022 의학물리 Vol.33 No.4
Recently, tetrahedral phantoms have been newly adopted as international standard mesh-type reference computational phantoms (MRCPs) by the International Commission on Radiological Protection, and a program has been developed to convert them to computational tomography images and DICOM-RT structure files for application of radiotherapy. Through this program, the use of the tetrahedral standard phantom has become available in clinical practice, but utilization has been difficult due to various library dependencies requiring a lot of time and effort for installation. To overcome this limitation, in this study a newly developed TET2DICOM-GUI, a TET2DICOM program based on a graphical user interface (GUI), was programmed using only the MATLAB language so that it can be used without additional library installation and configuration. The program runs in the same order as TET2DICOM and has been optimized to run on a personal computer in a GUI environment. A tetrahedron-based male international standard human phantom, MRCP-AM, was used to evaluate TET2DICOM-GUI. Conversion into a DICOM-RT dataset applicable in clinical practice in about one hour with a personal computer as a basis was confirmed. Also, the generated DICOM-RT dataset was confirmed to be effectively implemented in the radiotherapy planning system. The program developed in this study is expected to replace actual patient data in future studies.
Lee, Hanjin,Yeom, Yeon Soo,Nguyen, Thang Tat,Choi, Chansoo,Han, Haegin,Shin, Bangho,Zhang, Xujia,Kim, Chan Hyeong,Chung, Beom Sun,Zankl, Maria IOP 2019 Physics in medicine & biology Vol.64 No.4
<P>Recently, the Task Group 103 of the International Commission on Radiological Protection (ICRP) has developed new mesh-type reference computational phantoms (MRCPs) for adult male and female. When compared to the current voxel-type reference computational phantoms in ICRP Publication 110, the MRCPs have several advantages, including deformability which makes it possible to create phantoms in different body sizes or postures. In the present study, the MRCPs were deformed to produce a set of percentile-specific phantoms representing the 10th, 50th and 90th percentiles of standing height and body weight in Caucasian population. For this, anthropometric parameters for the percentile-specific phantoms were first derived from the anthropometric software and survey data. Then, the MRCPs were modified to match the derived anthropometric parameters. For this, first, the MRCPs were scaled in the axial direction to match the head height, torso length, and leg length. Then, the head, torso, and legs were scaled in the transversal directions to match the lean body mass for the percentile-specific phantoms. Finally, the scaled phantoms were manually adjusted to match the body weight and the remaining anthropometric parameters (upper arm, waist, buttock, thigh, and calf circumferences and sagittal abdominal diameter). The constructed percentile-specific phantoms and the MRCPs were implemented into the Geant4 Monte Carlo code to calculate organ doses for a cesium-137 contaminated floor. The results showed that organ doses of the 50th percentile (both standing height and body weight) phantoms are very close to those of the MRCPs. There were noticeable differences in organ doses, however, for the 10th and 90th percentile phantoms when compared with those of the MRCPs. The results of the present study confirm the general intuition that a small person receives higher doses than a large person when exposed to a static radiation field, and organs closer to the source receive higher doses.</P>