PDF(Pubmed)
Abstract：
Spectral photon-counting cone-beam computed tomography (CT) imaging is challenged by individual pixel response behaviours, which lead to noisy projection images and subsequent image artefacts like rings. Existing methods to correct for this either use calibration measurements, like signal-to-thickness calibration (STC), or perform a post-processing ring artefact correction of sinogram data or scan reconstructions without taking the pixel response explicitly into account. Here, we present a novel post-processing method (digital-to-analogue converter (DAC)-shifting) which explicitly measures the current pixel response using flat-field images and subsequently corrects the projection data. The DAC-shifting method was evaluated using a repeat series of the spectral photon-counting imaging (Medipix3) of a phantom with different density inserts and iodine K-edge imaging. The method was also compared against polymethyl methacrylate (PMMA)-based STC. The DAC-shifting method was shown to be effective in correcting individual pixel responses and was robust against detector instability; it led to a 47.4% average reduction in CT-number variation in homogeneous materials, with a range of 40.7-55.6%. On the contrary, the STC correction showed varying results; a 13.7% average reduction in CT-number variation, ranging from a 43.7% increase to a 45.5% reduction. In K-edge imaging, DAC-shifting provides a sharper attenuation peak and more uniform CT values, which are expected to benefit iodine concentration quantifications.
摘要：
光谱光子计数锥形束计算机断层扫描（CT）成像受到单个像素响应行为的挑战，这导致嘈杂的投影图像和随后的图像伪像环。现有的校正方法要么使用校准测量，如信号厚度校准（STC），或在不明确考虑像素响应的情况下对正弦图数据或扫描重建执行后处理环形伪影校正。这里,我们提出了一种新颖的后处理方法（数模转换器（DAC）移位），该方法使用平场图像明确地测量当前像素响应，然后校正投影数据。使用具有不同密度插入物的体模的光谱光子计数成像（Medipix3）的重复系列和碘K边缘成像来评估DAC移位方法。还将该方法与基于聚甲基丙烯酸甲酯(PMMA)的STC进行了比较。DAC移位方法被证明可以有效地校正单个像素响应，并且可以抵抗检测器的不稳定性；它导致均匀材料中CT数变化平均减少47.4％，范围为40.7-55.6%。相反,STC校正显示出不同的结果；CT数量变异平均减少13.7%，从43.7%的增长到45.5%的下降。在K边缘成像中，DAC移位提供更尖锐的衰减峰值和更均匀的CT值，预计将有利于碘浓度的量化。
