Accurate Image Reconstruction in Dual-Energy CT with Limited-Angular-Range Data Using a Two-Step Method.
Accurate Image Reconstruction in Dual-Energy CT with Limited-Angular-Range Data Using a Two-Step Method.
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DOI：
10.3390/bioengineering9120775
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发表时间：
2022-12-06
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双能CT （DECT）在有限角度范围内扫描（LARs）可以减少扫描时间和辐射剂量，并避免扫描仪的运动部件与成像物体之间可能发生的碰撞。波束硬化（BH）和LAR效应是使用LAR数据的DECT图像伪影的两个来源。在这项工作中，我们研究了一种两步方法来校正BH和LAR伪影，以便使用LAR数据在DECT中产生准确的图像重建。从DECT的低kvp和高kvp LAR数据中，我们首先使用数据域分解（DDD）算法获得校正了非线性BH效应的LAR基数据。然后，我们开发并定制了一种方向全变差（DTV）算法，从LAR基数据中重建得到的补偿了LAR效应的基图像。最后，利用重建的基础图像创建虚拟单色图像（VMIs），并估计成像对象内的碘浓度和有效原子序数等物理量。我们使用两个不同复杂程度和结构类型的数字幻影进行数值研究。低kvp和高kvp的LAR数据是由单弧（SA）和双正交弧（TOA） LARs上的幻影产生的，范围从。对所获得的VMIs进行目视检测和定量评价，结果表明，所提出的两步法得到的VMIs减少了BH和LAR伪影，提高了物理量的估计精度。此外，对于总LAR相同的SA和TOA扫描，后者显示出比前者更准确的图像和物理量估计。我们研究了一种两步方法，结合DDD和DTV算法来校正图像重建中的BH和LAR伪影，从DECT中的低kvp和高kvp LAR数据中产生准确的vmi和物理量估计。在LAR DECT精确图像重建工作中获得的结果和知识可能会进一步理解和洞察用于DECT应用的LAR扫描配置和重建程序的实际设计。
Dual-energy CT (DECT) with scans over limited-angular ranges (LARs) may allow reductions in scan time and radiation dose and avoidance of possible collision between the moving parts of a scanner and the imaged object. The beam-hardening (BH) and LAR effects are two sources of image artifacts in DECT with LAR data. In this work, we investigate a two-step method to correct for both BH and LAR artifacts in order to yield accurate image reconstruction in DECT with LAR data. From low- and high-kVp LAR data in DECT, we first use a data-domain decomposition (DDD) algorithm to obtain LAR basis data with the non-linear BH effect corrected for. We then develop and tailor a directional-total-variation (DTV) algorithm to reconstruct from the LAR basis data obtained basis images with the LAR effect compensated for. Finally, using the basis images reconstructed, we create virtual monochromatic images (VMIs), and estimate physical quantities such as iodine concentrations and effective atomic numbers within the object imaged. We conduct numerical studies using two digital phantoms of different complexity levels and types of structures. LAR data of low- and high-kVp are generated from the phantoms over both single-arc (SA) and two-orthogonal-arc (TOA) LARs ranging from to . Visual inspection and quantitative assessment of VMIs obtained reveal that the two-step method proposed can yield VMIs in which both BH and LAR artifacts are reduced, and estimation accuracy of physical quantities is improved. In addition, concerning SA and TOA scans with the same total LAR, the latter is shown to yield more accurate images and physical quantity estimations than the former. We investigate a two-step method that combines the DDD and DTV algorithms to correct for both BH and LAR artifacts in image reconstruction, yielding accurate VMIs and estimations of physical quantities, from low- and high-kVp LAR data in DECT. The results and knowledge acquired in the work on accurate image reconstruction in LAR DECT may give rise to further understanding and insights into the practical design of LAR scan configurations and reconstruction procedures for DECT applications.
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