Welch A, Gullberg G T, Christian P E, Datz F L, Morgan H T
University of Utah, Salt Lake City 84132, USA.
Med Phys. 1995 Oct;22(10):1627-35. doi: 10.1118/1.597422.
In this paper a method of modeling the distribution of scattered events in emission projection data is developed and applied. This method is based on the use of a transmission map to define the inhomogeneous scattering object. The key point is the use of the set of line integrals calculated as part of the attenuation correction technique, as the basis of a model of the distribution of scattered events. The probability of a photon being scattered through a given angle and being detected in the emission energy window is approximated using a Gaussian function. The parameters of this Gaussian are determined using Monte Carlo generated parallel-beam scatter line spread functions from a nonuniformly attenuating phantom. The model is incorporated into a two-dimensional projector-backprojector and used with the Expectation-Maximization-Maximum-Likelihood algorithm for the reconstruction of fan-beam phantom data. The correction is shown to perform well for a phantom that varies slowly in the axial direction. For the more clinically realistic situation of a torso phantom, the method produces improvements in terms of blood pool to myocardium contrast, but does not restore the contrast to the level exhibited in a reconstruction from "scatter free" data.
本文开发并应用了一种对发射投影数据中散射事件分布进行建模的方法。该方法基于使用传输图来定义非均匀散射物体。关键在于将作为衰减校正技术一部分计算的线积分集用作散射事件分布模型的基础。使用高斯函数近似光子以给定角度散射并在发射能量窗口中被检测到的概率。该高斯函数的参数通过蒙特卡罗方法从非均匀衰减体模生成的平行束散射线扩展函数来确定。该模型被纳入二维投影 - 反投影器中，并与期望最大化 - 最大似然算法一起用于扇形束体模数据的重建。结果表明，对于在轴向方向变化缓慢的体模，该校正效果良好。对于更接近临床实际情况的躯干体模，该方法在血池与心肌对比度方面有所改善，但未将对比度恢复到从“无散射”数据重建时所呈现的水平。
