Fourkal E, Li J S, Xiong W, Nahum A, Ma C M
Radiation Oncology Department, Fox Chase Cancer Center, 7701 Borehole Avenue, Philadelphia 19111, USA.
Phys Med Biol. 2003 Dec 21;48(24):3977-4000. doi: 10.1088/0031-9155/48/24/001.
In this paper we present Monte Carlo studies of intensity modulated radiation therapy using laser-accelerated proton beams. Laser-accelerated protons coming out of a solid high-density target have broad energy and angular spectra leading to dose distributions that cannot be directly used for therapeutic applications. Through the introduction of a spectrometer-like particle selection system that delivers small pencil beams of protons with desired energy spectra it is feasible to use laser-accelerated protons for intensity modulated radiotherapy. The method presented in this paper is a three-dimensional modulation in which the proton energy spectrum and intensity of each individual beamlet are modulated to yield a homogeneous dose in both the longitudinal and lateral directions. As an evaluation of the efficacy of this method, it has been applied to two prostate cases using a variety of beam arrangements. We have performed a comparison study between intensity modulated photon plans and those for laser-accelerated protons. For identical beam arrangements and the same optimization parameters, proton plans exhibit superior coverage of the target and sparing of neighbouring critical structures. Dose-volume histogram analysis of the resulting dose distributions shows up to 50% reduction of dose to the critical structures. As the number of fields is decreased, the proton modality exhibits a better preservation of the optimization requirements on the target and critical structures. It is shown that for a two-beam arrangement (parallel-opposed) it is possible to achieve both superior target coverage with 5% dose inhomogeneity within the target and excellent sparing of surrounding tissue.
在本文中，我们展示了使用激光加速质子束进行调强放射治疗的蒙特卡罗研究。从固体高密度靶中出射的激光加速质子具有宽广的能量和角度谱，导致剂量分布无法直接用于治疗应用。通过引入一种类似光谱仪的粒子选择系统，该系统可提供具有所需能谱的小质子笔形束，使用激光加速质子进行调强放射治疗是可行的。本文提出的方法是一种三维调制，其中对每个单独子束的质子能谱和强度进行调制，以在纵向和横向方向上产生均匀剂量。作为对该方法有效性的评估，已将其应用于两个前列腺病例，采用了多种射束排列方式。我们进行了调强光子计划与激光加速质子计划之间的比较研究。对于相同的射束排列和相同的优化参数，质子计划在靶区覆盖和邻近关键结构的保护方面表现更优。对所得剂量分布的剂量体积直方图分析表明，关键结构的剂量最多可降低50%。随着射野数量的减少，质子模态在靶区和关键结构的优化要求保持方面表现更好。结果表明，对于两射野排列（对穿），在靶区内剂量不均匀性为5%的情况下，可以实现优异的靶区覆盖以及对周围组织的良好保护。
