Interior micro-CT with an offset detector.
Interior micro-CT with an offset detector.
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DOI：
10.1118/1.4876724
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发表时间：
2014-06
期刊：
影响因子：
3.8
通讯作者：
K. Sen Sharma;H. Gong;Omid Ghasemalizadeh;Hengyong Yu;Ge Wang;Guohua Cao
中科院分区：
文献类型：
--
作者：
K. Sen Sharma;H. Gong;Omid Ghasemalizadeh;Hengyong Yu;Ge Wang;Guohua Cao
目的通过偏置探测器来增大微型计算机断层扫描(CT)系统的视场大小。增加的视场在许多应用中是有益的。然而，所有以前的研究都集中在这样的情况下，即在偏移探测器采集后增加的视场可以完全覆盖物体的横轴范围。在这里，作者研究了一个新的问题，其中微CT系统的视场虽然在偏移探测器采集后增加，但仍然覆盖对象内部的感兴趣区域(ROI)。方法采用偏移量探测器的面向内部感兴趣区域的Micro-CT扫描，由于探测器偏移量和投影截断的共同作用，造成重建困难。利用投影补全技术，将已有的三种重建方法从偏置探测器微型CT扩展到偏置探测器内部微型CT。然后，作者提出了一种新的方法，它结合了两种扩展的方法，使用了频率分割技术。作者分别在9.4%、18.8%、28.2%和37.6%的探测器偏移量下用模体模拟测试了这四种方法。作者还将这些方法应用于从定制的微型CT系统中以相同的探测器偏移量获取的物理模型数据集。结果当探测器偏移量较小时，各种重建方法均显示出较好的图像质量。在探测器偏移量较大的情况下，三种扩展方法要么有明显的阴影伪影，要么像素值偏差较大，而作者提出的方法在数值模拟和物理实验中都没有明显的伪影和像素值的最小偏差。结论对于带有偏移量探测器的内部微型CT，三种扩展重建方法在较小的探测器偏移量时表现良好，但在较大的探测器偏移量时表现出较强的伪影。当探测器偏移量较大时，通过抑制伪影和保持像素值，作者提出的重建方法的性能优于三种扩展的重建方法。
PURPOSE The size of field-of-view (FOV) of a microcomputed tomography (CT) system can be increased by offsetting the detector. The increased FOV is beneficial in many applications. All prior investigations, however, have been focused to the case in which the increased FOV after offset-detector acquisition can cover the transaxial extent of an object fully. Here, the authors studied a new problem where the FOV of a micro-CT system, although increased after offset-detector acquisition, still covers an interior region-of-interest (ROI) within the object. METHODS An interior-ROI-oriented micro-CT scan with an offset detector poses a difficult reconstruction problem, which is caused by both detector offset and projection truncation. Using the projection completion techniques, the authors first extended three previous reconstruction methods from offset-detector micro-CT to offset-detector interior micro-CT. The authors then proposed a novel method which combines two of the extended methods using a frequency split technique. The authors tested the four methods with phantom simulations at 9.4%, 18.8%, 28.2%, and 37.6% detector offset. The authors also applied these methods to physical phantom datasets acquired at the same amounts of detector offset from a customized micro-CT system. RESULTS When the detector offset was small, all reconstruction methods showed good image quality. At large detector offset, the three extended methods gave either visible shading artifacts or high deviation of pixel value, while the authors' proposed method demonstrated no visible artifacts and minimal deviation of pixel value in both the numerical simulations and physical experiments. CONCLUSIONS For an interior micro-CT with an offset detector, the three extended reconstruction methods can perform well at a small detector offset but show strong artifacts at a large detector offset. When the detector offset is large, the authors' proposed reconstruction method can outperform the three extended reconstruction methods by suppressing artifacts and maintaining pixel values.