Virtual scatter modulation for X-ray CT scatter correction using primary modulator.
Virtual scatter modulation for X-ray CT scatter correction using primary modulator.
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DOI：
10.3233/xst-17251
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发表时间：
2017
影响因子：
3
通讯作者：
Hewei Gao;Lei Zhu;R. Fahrig
中科院分区：
文献类型：
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作者：
Hewei Gao;Lei Zhu;R. Fahrig
提出了一种基于虚拟散射调制概念的X射线散射校正新算法，以减小散射估计中的混叠误差。虚拟散射调制可以通过将测量的原始调制图像除以测量的调制函数来实现。分割后，由于调制函数的非均匀性而引起的基色混叠的加剧，在很大程度上转化为散射的混叠。由于散射波的高频通常比一次波的高频低，因此预期其混叠的恶化程度较弱，因此可以减少总体混叠。在台式X射线锥束计算机断层扫描系统上扫描CatPhan©600体模和拟人胸部体模，以验证我们提出的算法。在Catphan体模上，在使用原始初级调制算法估计的Catphan散射轮廓的中心区域中清楚观察到的振荡，大部分被所提出的散射调制算法消除，从而在重建图像中产生更少的残留伪影和更好的CT数量均匀性。与使用初级调制算法时在选定的均匀区域中的38.9 HU的CT非均匀性相比，新算法将其显著降低至4.5 HU，达到与地面真实参考相同的均匀性水平。在胸部体模上，还实现了总体上更好的CT数均匀性。
A new scatter estimation algorithm with a concept of virtual scatter modulation for X-ray scatter correction using primary modulator is proposed to reduce the aliasing errors in the estimated scatter. Virtual scatter modulation can be realized through dividing the measured primary-modulated image by the measured modulation function. After the division, the aggravation of the aliasing of primary due to the non-uniformity of the modulation function is largely transferred to that of scatter. Since scatter in general has less high frequencies than primary does, the aggravation of its aliasing is expected to be weaker, and therefore the overall aliasing can be reduced. A CatPhan©600 phantom and an anthropomorphic thorax phantom are scanned on a tabletop X-ray cone-beam computed tomography system to validate our proposed algorithm. On the Catphan phantom, the oscillations that are clearly observed in the central region of the Catphan scatter profile estimated using the original primary-modulation algorithm, are mostly eliminated with the proposed scatter modulation algorithm, leading to less residual artifacts and better CT number uniformity in the reconstructed image. Compared with 38.9 HU of CT nonuniformity in a selected uniform region when the primary-modulation algorithm is used, the new algorithm significantly reduces it to 4.5 HU, reaching the same level of uniformity as the ground truth reference. On the thorax phantom, overall better CT number uniformity is also achieved.