Elshemey W M, Elsayed A A, El-Lakkani A
Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt.
Phys Med Biol. 1999 Dec;44(12):2907-15. doi: 10.1088/0031-9155/44/12/304.
Design of medical imaging devices based on the detection of low-angle coherent scattering is a subject of increasing interest. The technique is based on the differences in the distribution of photons coherently scattered from different body tissues. Coherent scattering is also useful in monitoring changes that may occur in a healthy tissue (e.g. carcinoma). In this work, low angle scattering properties of some tissues and tissue-equivalent materials are studied. Special care is given to the possibility of distinguishing between tissues of similar water content (e.g. muscle and blood). For this purpose, a Monte Carlo simulation is updated, introducing molecular form factor data, which include molecular interference effects. This program is used to simulate the angular distribution of scattered photons from two tissue-equivalent materials (lucite and water) and three biological samples (muscle, fat and blood). Simulation results agree well with previously measured angular distributions of scattered photons at 59.54 keV. Scattering from water and lucite is also measured at 8.047 keV. The effects of scattering geometry, sample thickness, incident photon energy and tissue type on the angular distribution of scattered photons are investigated. Results reveal the potential of measuring the full width at half maximum (FWHM) of the scattered photon distribution for tissue characterization. Energies up to 13 keV and sample thickness of 0.3 cm reported maximum differences between investigated samples. These conditions are expected to maximize the potential of using coherent scattering set-ups to monitor changes in biological samples even if their water contents are similar. Present results may act as a guide for the optimization of coherent scattering imaging systems.
基于低角度相干散射检测的医学成像设备设计是一个越来越受关注的课题。该技术基于从不同身体组织相干散射的光子分布差异。相干散射在监测健康组织（如癌组织）中可能发生的变化方面也很有用。在这项工作中，研究了一些组织和组织等效材料的低角度散射特性。特别关注区分水含量相似的组织（如肌肉和血液）的可能性。为此，更新了蒙特卡罗模拟，引入了包含分子干涉效应的分子形状因子数据。该程序用于模拟来自两种组织等效材料（有机玻璃和水）以及三个生物样本（肌肉、脂肪和血液）的散射光子的角分布。模拟结果与先前在59.54 keV下测量的散射光子角分布吻合良好。还在8.047 keV下测量了水和有机玻璃的散射。研究了散射几何形状、样品厚度、入射光子能量和组织类型对散射光子角分布的影响。结果揭示了测量散射光子分布的半高宽（FWHM）用于组织表征的潜力。高达13 keV的能量和0.3 cm的样品厚度报告了所研究样品之间的最大差异。即使生物样品的水含量相似，这些条件有望最大限度地发挥使用相干散射装置监测生物样品变化的潜力。目前的结果可为相干散射成像系统的优化提供指导。
