Department of Medical Physics, University of Florida, Gainesville, FL, USA.
J Appl Clin Med Phys. 2020 Dec;21(12):329-333. doi: 10.1002/acm2.13083. Epub 2020 Oct 30.
To generate a Cerenkov scatter function (CSF) for a primary proton beam and to study the dependence of the CSF on the irradiated medium.
The MCNP 6.2 code was used to generate the CSF. The CSF was calculated for light-pigmented, medium-pigmented, and dark-pigmented stratified skin, as well as for a homogeneous optical phantom, which mimics the optical properties of human tissue. CSFs were generated by binning all of the Cerenkov photons which escape the back end (end opposite beam incidence) of a 20 × 20 × 20 cm phantom. A 4 × 4 cm, 500 × 500 bin grid was used to create a histogram of the Cerenkov photon flux on the simulated medium's back surface (surface opposite beam incidence). A triple Gaussian was then used to fit the data.
From the triple Gaussian fit, the coefficients of the CSF for the four phantom materials was generated. The individual CSF fit coefficient errors, with respect to the Gaussian representation, were found to be between 0.92% and 4.11%. The R value for the fit was calculated to be 0.99. The phantom material was found to have a significant effect (63% difference between materials) on the CSF amplitude and full width at half maximum (195% difference between materials). The difference in these parameters for the three skin pigments was found to be small.
The CSF was obtained for a proton beam using the MCNP 6.2 code for a phantom constructed of light, medium, and dark stratified human skin, as well as for an optical phantom. The CSFs were then fit with a triple-Gaussian function. The coefficients can be used to generate a radially symmetric CSF, which can then be used to deconvolve a measured Cerenkov image to obtain the dose distribution.
生成初级质子束的切伦科夫散射函数（CSF），并研究 CSF 对辐照介质的依赖性。
使用 MCNP 6.2 代码生成 CSF。计算了光色素、中色素和暗色素分层皮肤以及模拟人体组织光学特性的同质光学模型的 CSF。通过将所有从 20×20×20 cm 模型后端（与束入射相对的末端）逃逸的切伦科夫光子进行 binning，生成 CSF。使用 4×4 cm、500×500 bin 网格在模拟介质的背面（与束入射相对的表面）创建切伦科夫光子通量的直方图。然后使用三高斯函数对数据进行拟合。
从三高斯拟合中，生成了四种模型材料的 CSF 拟合系数。相对于高斯表示，单个 CSF 拟合系数误差在 0.92%至 4.11%之间。拟合的 R 值计算为 0.99。发现模型材料对 CSF 幅度和半高全宽（材料之间差异为 195%）有显著影响（材料之间差异为 63%）。三种皮肤色素的这些参数之间的差异很小。
使用 MCNP 6.2 代码为由浅色、中色和深色分层人体皮肤以及光学模型构成的模型获得了质子束的 CSF。然后使用三高斯函数对 CSF 进行拟合。系数可用于生成径向对称的 CSF，然后可用于反卷积测量的切伦科夫图像以获得剂量分布。
