Time Resolved Cardiac Computed Tomography with Patient Dose Reduction

描述(申请人提供)：心血管疾病仍然是西方世界的主要死亡原因，给私人和公共卫生服务带来了越来越大的负担。心电门控心脏CT成像是早期发现冠状动脉脂肪易损斑块的一种很有前途的无创技术。然而，目前的技术存在两个主要问题：患者辐射剂量大和时间分辨率(TR)不足。目前，典型的辐射剂量为10-15次移动，是标准胸部CT扫描的3-5倍。目前的tr仅为80-165ms，而观察无运动伪影的跳动心脏运动所需的最小时间为10-30ms。当前技术使用心电信号来选择在放置在心动周期(例如，舒张期中期)的“安静”部分内的时间窗口中获取的投影数据。然后，通过忽略时间窗口内的心脏运动来重建图像，导致重建图像中的模糊和伪影。此外，这项技术只使用10%-30%的采集数据，并丢弃了其余的“异相”数据，导致患者受到不必要的辐射剂量。这项研究的长期目标是开发时间分辨的、低剂量的心脏CT成像。具体地说，我们将开发从测量数据估计心脏随时间变化的运动矢量场的算法，并将其集成到图像重建过程中。将通过最大化获取的4D投影数据和重建的时间分辨率4D图像之间的一致性来估计运动。由于对运动进行了补偿，图像质量将得到显著改善。此外，可以利用较低的管电流，因为所有采集的数据都将用于重建任何感兴趣的心脏时相。我们估计，患者的辐射剂量将减少到目前水平的50%-75%。我们的具体目标是：(1)开发研究该问题所需的计算机模拟工具；(2)开发集成运动估计和图像重建算法的新方法，用于时间分辨、低剂量心脏CT的应用；(3)结合患者和算法中使用的参数，对新算法的性能进行定量和定性的评估。所提出的方法不仅将解决目前运动模糊和辐射剂量过大的问题，而且还将使未来的心脏应用(例如，运动、灌注和狭窄之间的相关性)成为可能，这是目前的技术所不可能的。

DESCRIPTION (provided by applicant): Cardiovascular disease remains the leading cause of death in the western world, placing an ever-increasing burden on both private and public health services. The electrocardiogram (ECG)-gated cardiac CT imaging is a promising non-invasive technique for early detection of fatty vulnerable plaque in coronary arteries. However, there are two major problems with the current technique: large patient radiation dose and insufficient temporal resolution (TR). Currently, the typical radiation dose is 10-15 move, which is 3-5 times as large as a standard chest CT scan. The current TR is merely 80-165 ms in contrast to the minimum requirement of 10-30 ms to observe the beating heart motion without motion artifact. Current technique uses the ECG-signals to select projection data acquired in a time window that is placed within the "quiet" portion of the cardiac cycle (e.g., mid-diastole). Then, images are reconstructed by neglecting the cardiac motion within the time window resulting in blurring and artifacts in the reconstructed images. Also, this technique uses only 10-30% of the acquired data and throws away the rest of "off-phase" data, resulting in unnecessary radiation dose to the patient. The long-term goal of this research is to develop the time resolved, low dose cardiac CT imaging. Specifically, we will develop algorithms that estimate the time-dependent motion vector field of the heart from the measured data and integrate it into the image reconstruction process. The motion will be estimated by maximizing the agreement between the acquired 4D projection data and the reconstructed time-resolved 4D images. The quality of the image will be significantly improved since the motion is compensated. In addition, lower tube current could be utilized since all of the acquired data will be used to reconstruct any cardiac phase of interest. We estimate the reduction of radiation dose to the patient will be 50-75% of the current level. Our specific aims are: (1) to develop computer simulation tools necessary to study the problem, (2) to develop new methods that integrates the motion estimation and the image reconstruction algorithms for time resolved, low dose cardiac CT application, (3) to conduct the quantitative and qualitative evaluation of the performance of the new algorithms with various factors with patients and parameters used in the algorithms. The proposed methods will not only solve the current problems of motion blur and excessive radiation dose, but also enable future cardiac applications (e.g., correlation between the motion, perfusion and stenos is) that are not possible with the current techniques.