A digitally reconstructed radiograph algorithm calculated from first principles.
A digitally reconstructed radiograph algorithm calculated from first principles.
复制标题
根据第一原理计算的数字重建放射线照片算法。
DOI：
10.1118/1.4769413
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发表时间：
2013
期刊：
影响因子：
3.8
通讯作者：
Murphy,MartinJ
中科院分区：
文献类型：
--
作者：
Staub,David;Murphy,MartinJ
目的：开发一种算法，用于计算与真实的锥形束CT（CBCT）投影匹配的真实数字重建X线片（DRR），无需人工调整。方法：作者使用不同材料的锥形束CT投影X线片的测量衰减数据，获得一个将CT数转换为线性衰减系数（LAC）的函数。首先从衰减数据中去除散射、射束硬化和遮蔽眩光的影响。使用该转换函数，作者通过射线追踪算法计算了LAC通过CT沿着连接辐射源和探测器像素的射线的线积分，生成原始DRR。散射，射束硬化，和面纱眩光的影响，然后包括在DRR通过postprocessing.Results：作者比较实际CBCT投影DRR与所有校正（散射，射束硬化，和面纱眩光）和未校正的DRR。通过投影和DRR的视觉比较、像素强度比较、强度直方图比较以及DRR与投影像素强度的相关性图来评估算法准确度。一般来说，完全校正算法提供了一个小的，但不平凡的改进，在准确性上的未校正算法。作者还研究了用于确定射束硬化校正的基于测量和计算的方法，并发现基于计算的方法更上级，因为它考虑了不均匀的蝴蝶结滤波器厚度。作者对该算法的速度进行了基准测试，发现在射线步长为0.5 mm时，对于全探测器和CT分辨率，该算法在约0.35 s内产生DRR。结论：作者证明了根据第一原理计算的DRR算法，该算法考虑了散射、射束硬化和面纱眩光，以产生准确的DRR。该算法计算效率高，使其成为迭代CT重建技术的良好候选者，该技术需要基于DRR和投影的匹配的数据保真度项。
Purpose:To develop an algorithm for computing realistic digitally reconstructed radiographs (DRRs) that match real cone‐beam CT (CBCT) projections with no artificial adjustments.Methods:The authors used measured attenuation data from cone‐beam CT projection radiographs of different materials to obtain a function to convert CT number to linear attenuation coefficient (LAC). The effects of scatter, beam hardening, and veiling glare were first removed from the attenuation data. Using this conversion function the authors calculated the line integral of LAC through a CT along rays connecting the radiation source and detector pixels with a ray‐tracing algorithm, producing raw DRRs. The effects of scatter, beam hardening, and veiling glare were then included in the DRRs through postprocessing.Results:The authors compared actual CBCT projections to DRRs produced with all corrections (scatter, beam hardening, and veiling glare) and to uncorrected DRRs. Algorithm accuracy was assessed through visual comparison of projections and DRRs, pixel intensity comparisons, intensity histogram comparisons, and correlation plots of DRR‐to‐projection pixel intensities. In general, the fully corrected algorithm provided a small but nontrivial improvement in accuracy over the uncorrected algorithm. The authors also investigated both measurement‐ and computation‐based methods for determining the beam hardening correction, and found the computation‐based method to be superior, as it accounted for nonuniform bowtie filter thickness. The authors benchmarked the algorithm for speed and found that it produced DRRs in about 0.35 s for full detector and CT resolution at a ray step‐size of 0.5 mm.Conclusions:The authors have demonstrated a DRR algorithm calculated from first principles that accounts for scatter, beam hardening, and veiling glare in order to produce accurate DRRs. The algorithm is computationally efficient, making it a good candidate for iterative CT reconstruction techniques that require a data fidelity term based on the matching of DRRs and projections.