A fully four-dimensional, iterative motion estimation and compensation method for cardiac CT
A fully four-dimensional, iterative motion estimation and compensation method for cardiac CT
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DOI：
10.1118/1.4725754
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发表时间：
2012-07-01
期刊：
影响因子：
3.8
通讯作者：
Taguchi, Katsuyuki
中科院分区：
文献类型：
--
作者：
Tang, Qiulin;Cammin, Jochen;Taguchi, Katsuyuki
目的：提出一种新的全四维迭代心脏CT图像重建算法，该算法交替使用两种方法：从图像数据估计心脏随时间变化的运动矢量场(MVF)，以及利用估计的MVF和投影数据重建图像。运动估计(ME)和运动补偿图像重建(MCR)交替进行，直到达到收敛。ME方法使用心脏参考相和所有其他相之间的4D非刚性图像配准来估计心脏MVF。心脏的非刚性变形用三次B-样条法模拟。代价函数由加权差的平方和和空间和时间正则项组成。采用嵌套共轭梯度优化算法最小化代价函数，估计最大摄动系数。使用运动跟踪算法重建心脏图像，该算法利用ME方法估计的MVF。重建的图像为下一次迭代的ME提供输入。使用层析CT扫描仪采集的四组患者数据对所提出的方法的性能进行了评估。结果：随着迭代次数的增加，运动伪影明显减少，图像质量提高。在没有MCR的情况下，右冠状动脉(RCA)在轴位快速时相图像上变形成弧形。与舒张期静止期重建的RCA相比，该方法重建的RCA更清晰，重建的形状与静止期相似。使用所提出的算法，室间隔和右室之间的边界也更加清晰和尖锐。快速阶段(35%R-R)的转变范围陡度从6.8HU/像素增加到11.5HU/像素。ME-MCR算法只需4次迭代即可收敛。结论：我们提出了一种迭代交替使用ME和MCR算法的全4维图像重建方法。使用临床患者数据进行的性能测试减少了运动伪影。(C)2012年美国医学物理学家协会。[http://dx.doi.org/10.1118/1.4725754]
Purpose: To develop a new fully four-dimensional (4D), iterative image reconstruction algorithm for cardiac CT that alternates the following two methods: estimation of a time-dependent motion vector field (MVF) of the heart from image data and reconstruction of images using the estimated MVF and projection data.Methods: Volumetric image data at different cardiac phase points were obtained using electrocardiogram-gated CT. Motion estimation (ME) and motion-compensated image reconstruction (MCR) were performed alternately until convergence was achieved. The ME method estimated the cardiac MVF using 4D nonrigid image registration between a cardiac reference phase and all the other phases. The nonrigid deformation of the heart was modeled using cubic B-splines. The cost function consisted of a sum of squared weighted differences and spatial and temporal regularization terms. A nested conjugate gradient optimization algorithm was applied to minimize the cost function and estimate the MVFs. Cardiac images were reconstructed using a motion-tracking algorithm that utilized the MVFs estimated by the ME method. The reconstructed images supplied the input to the ME of the next iteration. The performance of the proposed method was evaluated using four patient data sets acquired with a 64-slice CT scanner. The heart rates of the patients ranged from 52 to 71 beats/min.Results: Motion artifacts were significantly reduced, and the image quality increased with the number of iterations. Without MCR, the right coronary artery (RCA) was deformed into an arc in axial images of rapid phases. With the proposed method the RCA appeared sharper and was reconstructed similar in shape to the reconstruction at the quiescent phase at mid-diastole. The boundary between the interventricular septum and the right ventricle was also clearer and sharper using the proposed algorithm. The steepness of the transition range at a rapid phase (35% R-R) was increased from 6.8 HU/pixel to 11.5 HU/pixel. The ME-MCR algorithm converged in just four iterations.Conclusion: We developed a fully 4D image reconstruction method that alternates ME and MCR algorithms in an iterative fashion. Performance tests using clinical patient data resulted in reduced motion artifacts. (C) 2012 American Association of Physicists in Medicine. [http://dx.doi.org/10.1118/1.4725754]