ABSTRACT

A modified semi-empirical formula that relates the maximum range of the positron to the strength of different magnetic field strengths is developed via Monte Carlo simulation. The formula is derived as an extension to the existing formula of no magnetic field. COMSOL Multiphysics is used to simulate the different physics, including electromagnetic physics and charged particle tracking physics. The Monte Carlo simulation technique by COMSOL is employed to study the effect of magnetic field strength on the positron range PET/MRI scan of the head’s tumor. The magnetic field varies in the range 1–10 Tesla. The simulation code using positron emission is conducted by the Monte Carlo method. Simulation results show that changing the magnetic field affects the particle trajectory and hence the maximum positron range. The elliptic trajectory causes a reduction in displacement between the original location of emission and the location of annihilation, which permits an increased photon emission per unit volume of the tumor and hence a better image resolution. The main contribution of the paper is the formulation of a new semi-empirical relation taking into account the presence of a magnetic field by simulating different particle trajectories for the different magnetic field strengths.

摘要

通过蒙特卡罗模拟，建立了一个修正的半经验公式，该公式将正电子的最大范围与不同磁场强度的强度相关联。该公式是对现有无磁场公式的扩展。COMSOL Multiphysics用于模拟不同的物理学，包括电磁物理学和带电粒子跟踪物理学。采用COMSOL公司的Monte Carlo模拟技术研究磁场强度对头部肿瘤的正电子PET / MRI扫描的影响。磁场的变化范围是1–10 Tesla。使用正电子发射的模拟代码通过蒙特卡洛方法进行。仿真结果表明，改变磁场会影响粒子轨迹，从而影响最大正电子范围。椭圆轨迹使发射的原始位置和an灭的位置之间的位移减小，这允许增加单位肿瘤体积的光子发射，从而获得更好的图像分辨率。本文的主要贡献是通过针对不同的磁场强度模拟不同的粒子轨迹，考虑了磁场的存在，提出了一种新的半经验关系式。