IEEE Trans Med Imaging. 2017 May;36(5):1151-1161. doi: 10.1109/TMI.2017.2654508. Epub 2017 Jan 17.
Even though the X-ray Computed Tomography (CT) scan is considered suitable for fast imaging, motion-artifact-free cardiac imaging is still an important issue, because the gantry rotation speed is not fast enough compared with the heart motion. To obtain a heart image with less motion artifacts, a motion estimation (ME) and motion compensation (MC) approach is usually adopted. In this paper, we propose an ME/MC algorithm that can estimate a nonlinear heart motion model from a sinogram with a rotation angle of less than 360°. In this algorithm, we first assume the heart motion to be nonrigid but linear, and thereby estimate an initial 4-D motion vector field (MVF) during a half rotation by using conjugate partial angle reconstructed images, as in our previous ME/MC algorithm. We then refine the MVF to determine a more accurate nonlinear MVF by maximizing the information potential of a motion-compensated image. Finally, MC is performed by incorporating the determined MVF into the image reconstruction process, and a time-resolved heart image is obtained. By using a numerical phantom, a physical cardiac phantom, and an animal data set, we demonstrate that the proposed algorithm can noticeably improve the image quality by reducing motion artifacts throughout the image.
尽管 X 射线计算机断层扫描 (CT) 被认为适合快速成像，但无运动伪影的心脏成像仍然是一个重要问题，因为与心脏运动相比，机架旋转速度不够快。为了获得运动伪影较少的心脏图像，通常采用运动估计 (ME) 和运动补偿 (MC) 方法。在本文中，我们提出了一种 ME/MC 算法，该算法可以从旋转角度小于 360°的射线图估计非线性心脏运动模型。在该算法中，我们首先假设心脏运动是非刚性的但线性的，因此通过使用共轭部分角度重建图像，如我们之前的 ME/MC 算法中那样，在半旋转期间估计初始的 4-D 运动矢量场 (MVF)。然后，我们通过最大化运动补偿图像的信息势来细化 MVF，以确定更准确的非线性 MVF。最后，通过将确定的 MVF 合并到图像重建过程中进行 MC，并获得时间分辨的心脏图像。通过使用数值体模、物理心脏体模和动物数据集，我们证明该算法可以通过减少整个图像中的运动伪影来显著提高图像质量。
