Scatter correction method for x-ray CT using primary modulation: Phantom studies
Scatter correction method for x-ray CT using primary modulation: Phantom studies
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DOI：
10.1118/1.3298014
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发表时间：
2010-02-01
期刊：
影响因子：
3.8
通讯作者：
Zhu, Lei
中科院分区：
文献类型：
--
作者：
Gao, Hewei;Fahrig, Rebecca;Zhu, Lei
方法：首先分析一次调制法估计散射的潜在误差。在两个桌面CT系统上，使用三个体模研究该方法：Catphan（C）600体模、拟人胸部体模和具有两个环的Catphan（C）600体模。两个不同的主调制器也被设计来显示调制器参数对散射校正效率的影响。结果：在Catphan（C）600体模上，该方法使感兴趣区CT值的误差从371.4降到21.9;对比噪声比也从10.9增加到19.2。在第二项研究中的拟人胸部体模上，由于高散射信号和对象异质性，该方法将所选ROI中CT数的误差从327 HU降低到19 HU，并将总体平均值的误差从31.4%降低到5.7%。第三项研究是调查对象大小对我们方法效率的影响。Catphan（C）600体模（无任何环）上的散射-原发比估计误差（直径20 cm）的水平为0.04，在椭圆环体模上上升至0.07和0.1（短轴30 cm，长轴38 cm），并有一个圆环结论：在三个体模研究中，使用图像比较和定量分析证明了所提出的方法具有良好的散射校正性能。理论和实验表明，具有低透射因子和高调制频率的强初级调制对于高散射校正精度是优选的。
Methods: The authors first analyze the potential errors of the estimated scatter in the primary modulation method. On two tabletop CT systems, the method is investigated using three phantoms: A Catphan(C)600 phantom, an anthropomorphic chest phantom, and the Catphan(C)600 phantom with two annuli. Two different primary modulators are also designed to show the impact of the modulator parameters on the scatter correction efficiency. The first is an aluminum modulator with a weak modulation and a low modulation frequency, and the second is a copper modulator with a strong modulation and a high modulation frequency.Results: On the Catphan(C)600 phantom in the first study, the method reduces the error of the CT number in the selected regions of interest (ROIs) from 371.4 to 21.9 Hounsfield units (HU); the contrast to noise ratio also increases from 10.9 to 19.2. On the anthropomorphic chest phantom in the second study, which represents a more difficult case due to the high scatter signals and object heterogeneity, the method reduces the error of the CT number from 327 to 19 HU in the selected ROIs and from 31.4% to 5.7% on the overall average. The third study is to investigate the impact of object size on the efficiency of our method. The scatter-to-primary ratio estimation error on the Catphan(C)600 phantom without any annulus (20 cm in diameter) is at the level of 0.04, it rises to 0.07 and 0.1 on the phantom with an elliptical annulus (30 cm in the minor axis and 38 cm in the major axis) and with a circular annulus (38 cm in diameter).Conclusions: On the three phantom studies, good scatter correction performance of the proposed method has been demonstrated using both image comparisons and quantitative analysis. The theory and experiments demonstrate that a strong primary modulation that possesses a low transmission factor and a high modulation frequency is preferred for high scatter correction accuracy.