Recent Advances in Computational Human Phantom for Monte Carlo Dose Calculation

Abstract

In the present paper, an advanced type of a computational human phantom called PSRK-Man (Polygon Surface Reference Korean-Man) is introduced with its advantages over the traditional voxel phantom. This paper also discusses the computation speed issue of the surface phantom and the implementation of the direct accelerated geometry Monte Carlo (DAGMC) toolkit in Geant4, which makes the computation speed of the surface phantom by 20-30 times. With the computation speed problem solved, the surface phantom can be used in many applications, including medical imaging, accurate charged particle dosimetry, and radiation therapy simulations.MG[YQTFU<"rqn{iqp"uwthceg"rjcpvqo."Oqpvg"Ectnq."FCIOE."Igcpv6" K0"Kpvtqfwevkqp"The computational human phantom (CHP) is a numerical model of a human body that can be used in computer simulations. Hkiwtg" 3 shows a brief history of CHPs. First, simple geometric forms such as spheres, cylinders, or boxes were used to represent the human body. Then, more complicated models, called stylized or mathematical phantom, were developed to represent the human body 1) . Then, finally, since 1984, people started to use the voxel phantoms 1) . The voxel phantoms are developed using tomography images of human bodies, like CT or MRI, and therefore these describe the human bodies much more realistically than a stylized phantom.The voxel phantoms, however, have some limitations. First, the voxel phantoms are not deformable and therefore it is very difficult, if not possible, to modify the posture of the phantom or the shape of the organs in the phantoms. The *Corresponding Author, E-mail:chkim@hanyang.ac.kr voxel phantoms also show stair-stepped surfaces and it is not suitable for medical imaging simulation because these steps will appear on simulated images which do not really exist on real images. It is also very difficult to model very thin or complicated structures such as oral mucosa, skin, eye balls, and internal ears.On the other hand, a surface phantom, a polygon-mesh phantom or a NURBS phantom, does not have the aforementioned problems. Indeed, a surface phantom is freely deformable and therefore the shape of the phantom or internal organs can be easily changed. Four-dimensional (4D) Monte Carlo simulation is feasible; that is, we can transport the (radiation) particles during the movement of the organs in a patient due to cardiac or respiratory actions, or during the movement of a radiation worker in a radiation field. The surface phantom can easily model very thin structures such as oral mucosa and skin, which are ARTICLE

A Review of Numerical Simulation and Analytical Modeling for Medical Devices Safety in MRI

“…Two main phantom types exist: voxel phantoms and surface phantoms. The first ones are voxelled, staircased models, whereas the surface models have smoother surfaces, can be meshed at one's convenience and have a high resolution that is essential when fine body structures are studied [12].…”