Primak A N, Dong Y, Dzyubak O P, Jorgensen S M, McCollough C H, Ritman E L
CT Clinical Innovation Center, Department of Radiology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
Med Phys. 2007 Dec;34(12):4726-37. doi: 10.1118/1.2805476.
Quantitative evaluation of cardiac image data obtained using multidetector row computed tomography (CT) is compromised by partial scan reconstructions, which improve the temporal resolution but significantly increase image-to-image CT number variations for a fixed region of interest compared to full reconstruction images. The feasibility of a new approach to solve this problem is assessed. An anthropomorphic cardiac phantom and an anesthetized pig were scanned on a dual-source CT scanner using both full and partial scan acquisition modes under different conditions. Additional scans were conducted with the electrocardiogram (ECG) signal being in synchrony with the gantry rotation. In the animal study, a simple x-ray detector was used to generate a signal once per gantry rotation. This signal was then used to pace the pig's heart. Phantom studies demonstrated that partial scan artifacts are strongly dependent on the rotational symmetry of angular projections, which is determined by the object shape and composition and its position with respect to the isocenter. The degree of partial scan artifacts also depends on the location of the region of interest with respect to highly attenuating materials (bones, iodine, etc.) within the object. Single-source partial scan images (165 ms temporal resolution) were significantly less affected by partial scan artifacts compared to dual-source partial scan images (82 ms temporal resolution). When the ECG signal was in synchrony with the gantry rotation, the same cardiac phase always corresponded to the same positions of the x-ray tube(s) and, hence, the same scattering and beam hardening geometry. As a result, the range of image-to-image CT number variations for partial scan reconstruction images acquired in synchronized mode was decreased to that achieved using full reconstruction image data. The success of the new approach, which synchronizes the ECG signal with the position of the x-ray tube(s), was demonstrated both in the phantom and animal experiments.
使用多排探测器计算机断层扫描（CT）获得的心脏图像数据的定量评估受到部分扫描重建的影响，部分扫描重建提高了时间分辨率，但与全重建图像相比，对于固定感兴趣区域，显著增加了图像间CT值的变化。评估了一种解决该问题的新方法的可行性。在不同条件下，使用全扫描和部分扫描采集模式，在双源CT扫描仪上对拟人化心脏模型和麻醉猪进行扫描。在心电图（ECG）信号与机架旋转同步的情况下进行了额外的扫描。在动物研究中，使用一个简单的X射线探测器在每次机架旋转时产生一次信号。然后该信号用于刺激猪的心脏。模型研究表明，部分扫描伪影强烈依赖于角度投影的旋转对称性，这由物体形状、组成及其相对于等中心的位置决定。部分扫描伪影的程度还取决于感兴趣区域相对于物体内高衰减物质（骨骼、碘等）的位置。与双源部分扫描图像（82毫秒时间分辨率）相比，单源部分扫描图像（165毫秒时间分辨率）受部分扫描伪影的影响明显较小。当ECG信号与机架旋转同步时，相同的心脏相位总是对应于X射线管的相同位置，因此，对应于相同的散射和束硬化几何形状。结果，同步模式下采集的部分扫描重建图像的图像间CT值变化范围减小到使用全重建图像数据时所达到的范围。在模型和动物实验中均证明了将ECG信号与X射线管位置同步的新方法的成功。
