Molière maximum likelihood proton path estimation approximated by cubic Bézier curve for scatter corrected proton CT reconstruction.
Molière maximum likelihood proton path estimation approximated by cubic Bézier curve for scatter corrected proton CT reconstruction.
复制标题
莫里哀最大似然质子路径估计通过三次贝塞尔曲线近似，用于散射校正质子 CT 重建。
DOI：
10.1088/1361-6560/ab9413
复制
发表时间：
2020
影响因子：
3.5
通讯作者：
Lazos D
中科院分区：
文献类型：
--
作者：
Lazos D
本文提出了一种计算质子CT中被扫描物体内部质子路径的极大似然法。莫里哀理论是第一次用来推导一个物理模型，描述质子多重库仑散射，避免了目前使用的高斯近似的需要。为了实现这一点，所提出的方法使用三次贝塞尔曲线来逼近质子路径，然后基于莫里哀模型通过参数优化来最大化路径可能性。从高地公式为基础的高斯近似的结果也进行了比较。单纯形法用于优化。通过从在代数重建过程的每次迭代时计算/更新的阻止能力图适当地计算散射参数，来考虑扫描对象的材料的散射特性。质子径迹长度的限制所施加的质子能量损失占。该方法也适用于没有测量出射角数据的情况。Geant 4 Monte Carlo模拟用于模型验证。我们的研究结果表明，使用莫里哀概率密度函数建模的多次库仑散射提出了一个温和的2%的精度提高高斯近似和最可能的路径方法。体素化体模的模拟显示，将材料信息纳入优化中没有本质的益处，而具有能量约束的路径优化略微增加了骨/水界面体模中的路径分辨率。方法误差被发现依赖于能量，质子轨道长度内的介质，和数据过滤的比例。
A maximum likelihood approach to the problem of calculating the proton paths inside the scanned object in proton computed tomography is presented. Molière theory is used for the first time to derive a physical model that describes proton multiple Coulomb scattering, avoiding the need for the Gaussian approximation currently used. To enable this, the proposed method approximates proton paths with cubic Bézier curves and subsequently maximizes the path likelihood through parametric optimization, based on the Molière model. Results from the Highland formula-based Gaussian approximation are also presented for comparison. The simplex method is utilized for optimisation. The scattering properties of the material (s) of the scanned object are taken into account by appropriately calculating the scattering parameters from the stopping power map that is calculated/updated at every iteration of the algebraic reconstruction process. Proton track length constraint imposed by the proton energy loss is accounted for. The method is also applied in the case that no exit angle data are measured. Geant4 Monte Carlo simulations were performed for model validation. Our results show that use of Molière probability density function for modelling the multiple Coulomb scattering presents a modest 2% accuracy improvement over the Gaussian approximation and most-likely-path method. Simulations of voxelized phantom showed no essential benefit from the inclusion of the material information into the optimization, while path optimization with energy constraint slightly increased path resolution in a bone/water interface phantom. Method error was found to depend on energy, proton track-length within the medium, and proportion of data filtering.