TH‐D‐351‐06: Comparison Between 2D Monte Carlo Modeled and Experimental Cone‐Beam CT X‐Ray Projections
TH‐D‐351‐06: Comparison Between 2D Monte Carlo Modeled and Experimental Cone‐Beam CT X‐Ray Projections
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TH-D-351-06：二维蒙特卡罗模型与实验锥束 CT X 射线投影之间的比较
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Williamson
中科院分区：
文献类型：
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作者：
D. Lazos;D. Pokhrel;Z. Su;J. Lu;J. Williamson
目的：对锥束CT(CBCT)X射线投影数据进行快速准确的建模，可以通过在图像重建之前对投影数据进行调整，或者通过支持对竞争的图像重建和处理算法进行严格的仿真研究来提高锥束CT(CBCT)的图像质量。在这项研究中，我们比较了蒙特卡罗计算的X射线投影和从我们的瓦里安三部曲CBCT成像系统中实验获得的已知设计的模体的投影。方法和材料：我们最近开发的蒙特卡罗光子传输程序PTRAN用于计算已知直径的圆柱形体模(CatPhan和NA型号76-410)的初级和散射投影，包括全扇和半扇几何形状的蝴蝶结滤光片和反散射网格。模拟是基于测量的120 kVp谱、光束分布和平板探测器(4030CB)的点扩展函数。利用波束停止阵列法从OBI图像中获取散射和SPR分布。由于探测器PSF尾部较长，散射测量的偏差可通过铅掩模或去卷积进行校正。结果：模拟的一次轮廓与实验符合在3%以内，而模拟的散射轮廓符合在8%-10%之间。PSF测量和掩模测量都表明，散射辐射值可能会受到高达7%的探测器PSF尾部的偏差。结论：模拟投影数据与实测投影数据的误差在6-8%量级，与文献相符。较高的测量精度主要通过改进束流模型和校正探测器PSF引起的非线性来实现。该项目部分得到了瓦里安医疗系统公司和美国国立卫生研究院的资助(R01，CA，75371)。
Purpose: Fast and accurate modeling of cone‐beam CT(CBCT) x‐ray projection data can improve cone‐beam CT(CBCT)image quality either by conditioning projection data prior to image reconstruction or by supporting rigorous comparative simulation studies of competing image reconstruction and processing algorithms. In this study, we compare Monte Carlo‐ computed x‐ray projections with projections experimentally acquired from our Varian Trilogy CBCTimaging system for phantoms of known design. Method and Materials: Our recently developed Monte Carlo photon‐transport code, PTRAN, was used to compute primary and scatter projections for cylindrical phantoms of known diameter (CatPhan and NA model 76‐410) with and without bow‐tie filter and antiscatter grid for both full‐ and half‐fan geometries. The simulations were based upon measured 120 kVp spectra, beam profiles, and flat‐panel detector (4030CB) point‐spread functions. The beam‐stop array method was used to acquire scatter and SPR distributions from the OBI images. The biasing of scatter measurements due to the long detector PSF tails was corrected either by a lead mask or by deconvolution. Computed projections were compared to flat‐ and dark‐field corrected 4030CB images.Results: The simulated primary profiles agree with experiment within 3%, while the simulated scatter profiles agree within 8–10%. Both PSF measurements and mask measurements indicate that scatter radiation values can be biased by as much as 7% detector PSF tails. Conclusion: In agreement with the literature, the difference between simulated and measured projection data is of the order of 6–8%. Higher accuracy can be achieved mainly by improving the beam modeling and correcting the non linearities induced by the detector PSF. This project was supported in part by grants from Varian Medical Systems and NCI (R01 CA 75371).