Cardiac motion correction based on partial angle reconstructed images in x-ray CT
Cardiac motion correction based on partial angle reconstructed images in x-ray CT
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DOI：
10.1118/1.4918580
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发表时间：
2015-05-01
期刊：
影响因子：
3.8
通讯作者：
Ra, Jong Beom
中科院分区：
文献类型：
--
作者：
Kim, Seungeon;Chang, Yongjin;Ra, Jong Beom
目的：心脏x线CT成像由于心脏运动仍然具有挑战性，即使以目前设备的转速也不能忽视。因此，已经开发了许多算法，通过使用投影数据或重建图像估计运动来补偿剩余的运动伪影。在这些算法中，准确的运动估计是补偿图像质量的关键。此外，由于扫描范围与辐射剂量直接相关，因此在运动估计中最好将扫描范围最小化。本文提出了一种基于旋转角度小于360度的正弦图的运动估计和补偿算法，该算法利用两幅相对的三维部分角度重构（PAR）图像来估计整个心脏区域的运动，并在重建过程中补偿运动。方法：CT系统在180度+ α + β的角度范围内扫描胸部区域，包括心脏，其中A和β分别表示检测器风扇角度和额外的局部角度。获得的锥束投影数据通过行向fano -parallel重划转换为锥平行几何。两幅中心投影角相隔180度的共轭三维PAR图像，重建的角度范围为β，比180度+ α的短扫描范围小得多。虽然这些图像包括有限的视角伪影，干扰准确的运动估计，但它们具有比短扫描图像更好的时间分辨率。因此，在对这些伪影进行预处理后，作者通过图像之间的非刚性配准来估计整个视场在半旋转期间的运动模型。最后，结合估计的运动模型，在目标阶段进行运动补偿图像重建。目标相位选择为与两个共轭PAR图像的中心视角正交的视角所对应的相位。为了评估所提出的算法，使用了数字XCAT和物理动态心脏幻影数据集。通过假设系统旋转时间为300 ms， XCAT幻影数据集分别在心率为70和100 bpm时生成。使用慢速旋转的XCT系统扫描物理动态心脏幻影，当系统转速为300毫秒时，有效心率为70 bpm。结果：在XCAT幻影实验中，从所提出的算法获得的运动补偿3D图像显示，冠状动脉在所有阶段的运动伪影都更少。此外，被运动污染的物体边界得到了很好的恢复。尽管物体的位置和边界形状在某些情况下仍然与地面真实情况有所不同，但作者发现冠状动脉的可见性明显提高，运动伪影大大减少。物理幻像研究也表明，运动补偿图像的视觉质量得到了很大的改善。结论：提出了一种新的基于PAR图像的心脏运动估计和补偿算法。该算法需要小于360度的角度扫描范围，并通过数字XCAT和物理动态心脏幻影数据集证明了该算法的优异性能。(C) 2015年美国医学物理学家协会。
Purpose: Cardiac x-ray CT imaging is still challenging due to heart motion, which cannot be ignored even with the current rotation speed of the equipment. In response, many algorithms have been developed to compensate remaining motion artifacts by estimating the motion using projection data or reconstructed images. In these algorithms, accurate motion estimation is critical to the compensated image quality. In addition, since the scan range is directly related to the radiation dose, it is preferable to minimize the scan range in motion estimation. In this paper, the authors propose a novel motion estimation and compensation algorithm using a sinogram with a rotation angle of less than 360 degrees The algorithm estimates the motion of the whole heart area using two opposite 3D partial angle reconstructed (PAR) images and compensates the motion in the reconstruction process.Methods: A CT system scans the thoracic area including the heart over an angular range of 180 degrees + alpha + beta, where a and beta denote the detector fan angle and an additional partial angle, respectively. The obtained cone-beam projection data are converted into cone-parallel geometry via row-wise fanto-parallel rebinning. Two conjugate 3D PAR images, whose center projection angles are separated by 180 degrees, are then reconstructed with an angular range of beta, which is considerably smaller than a short scan range of 180 degrees + alpha. Although these images include limited view angle artifacts that disturb accurate motion estimation, they have considerably better temporal resolution than a short scan image. Hence, after preprocessing these artifacts, the authors estimate a motion model during a half rotation for a whole field of view via nonrigid registration between the images. Finally, motion-compensated image reconstruction is performed at a target phase by incorporating the estimated motion model. The target phase is selected as that corresponding to a view angle that is orthogonal to the center view angles of two conjugate PAR images. To evaluate the proposed algorithm, digital XCAT and physical dynamic cardiac phantom datasets are used. The XCAT phantom datasets were generated with heart rates of 70 and 100 bpm, respectively, by assuming a system rotation time of 300 ms. A physical dynamic cardiac phantom was scanned using a slowly rotating XCT system so that the effective heart rate will be 70 bpm for a system rotation speed of 300 ms.Results: In the XCAT phantom experiment, motion-compensated 3D images obtained from the proposed algorithm show coronary arteries with fewer motion artifacts for all phases. Moreover, object boundaries contaminated by motion are well restored. Even though object positions and boundary shapes are still somewhat different from the ground truth in some cases, the authors see that visibilities of coronary arteries are improved noticeably and motion artifacts are reduced considerably. The physical phantom study also shows that the visual quality of motion-compensated images is greatly improved.Conclusions: The authors propose a novel PAR image-based cardiac motion estimation and compensation algorithm. The algorithm requires an angular scan range of less than 360 degrees The excellent performance of the proposed algorithm is illustrated by using digital XCAT and physical dynamic cardiac phantom datasets. (C) 2015 American Association of Physicists in Medicine.