Weinhous M S, Nath R, Schulz R J
Med Phys. 1985 Sep-Oct;12(5):598-603. doi: 10.1118/1.595681.
A Monte Carlo electron-photon transport code was developed in order to determine the effects of static, longitudinal, magnetic fields on dose distributions produced by high-energy electron beams, and to optimize the design of a superconducting magnet system. As a result of these simulations, a 20-cm-i.d., 30-cm-o.d., 15-cm-tall, single-coil, magnet system was designed that could be incorporated into a mobile treatment table for use with a standard radiation therapy accelerator. Operating at a current density of 18 kA/cm2, the magnet would produce field strengths of 1-4 T in the phantom and 0.01 T at the accelerator exit window. Magnetically enhanced dose distributions, calculated for 20- and 30-MeV electron beams, show a pronounced Bragg peak, steeper gradients to the sides and rear, and a roughly fourfold increase in the peak dose to entrance dose ratios relative to those similarly calculated without a magnetic field. These magnetically enhanced dose distributions have the potential for sparing intervening tissue when high-energy electrons are used for the treatment of deep-seated tumors.
为了确定静态纵向磁场对高能电子束产生的剂量分布的影响，并优化超导磁体系统的设计，开发了一种蒙特卡罗电子-光子输运代码。通过这些模拟，设计了一个内径20厘米、外径30厘米、高15厘米的单线圈磁体系统，该系统可集成到移动治疗台上，与标准放射治疗加速器配合使用。该磁体在电流密度为18 kA/cm²的情况下运行，在模体中产生的场强为1-4 T，在加速器出口窗口处为0.01 T。针对20 MeV和30 MeV电子束计算的磁增强剂量分布显示出明显的布拉格峰，向侧面和后方的梯度更陡，并且相对于无磁场时类似计算的峰剂量与入射剂量比大致增加了四倍。当使用高能电子治疗深部肿瘤时，这些磁增强剂量分布有可能使中间组织免受辐射。
