Ultrafast Z-Scan X-ray Volume CT

描述(由申请人提供)： 目前的计算机断层扫描系统提供有限的时间分辨率。当患者床位穿过狭窄的暴露区域时，大的空间覆盖率需要连续采集切片。对于螺旋CT扫描仪和电子束CT(EBCT)来说也是如此。这有几个后果。对于对比剂增强血管造影研究或肿瘤对比剂摄取的研究，在任何解剖位置都几乎没有可用的动态信息，并且相对于对比剂到达的时间可能因患者而异。对于冠状动脉成像，即使在使用EBCT的情况下，在每个切片的采集期间采集大量的角度数据扇区的需要导致在采集时间期间冠状动脉运动大约50毫秒，即使使用EBCT也是如此。未能按照顺序心跳适当推进该部门，可能会导致角度抽样不足和技术上不可接受的检查。 最近，几个小组已经开始研究体积CT系统，使用传统的X射线管在单个圆形路径上旋转，与相对的平板X射线探测器结合工作台运动。虽然这增加了有用的探测立体角，但它不能为大视场上的动态成像提供最佳的源轨迹。 我们建议研究一种先进的CT系统的可行性，在该系统中，X射线焦点在机架旋转(Z-SCAN)过程中沿患者的长度(Z-维度)快速变化。这将通过扫描电子束或离散焦点的线性阵列来实现，从而产生与大型探测器阵列相对的锥形束源的灵活分布。源轨迹可以针对特定的临床应用进行优化。任意源轨迹的可用性将允许在没有明显台面运动的情况下对造影剂动力学进行大容量动态时间分辨检测，并且对于冠状动脉成像，将允许在每个心动期进行较短的曝光时间。 我们将研究MRI采集计划对X射线CT的扩展，这些计划使我们能够以比传统笛卡尔MRI快40倍的速度获得对比度增强的MR图像。 在R21阶段，将通过仿真来研究基于所提出的方法的系统的潜在性能。测量和图像重建将使用X射线试验台来产生，在该试验台中将移动传统的源以模拟预期的源轨迹。在R33阶段，将开发一种采用扫描电子束技术或分布式脉冲源的源试验台。 预期的扫描仪的潜在应用包括肿瘤对比剂摄取的动态研究、时间分辨CT血管成像和冠状动脉成像。我们将专注于后两种应用，并将在所提出的研究的基础上，开发基于Z-扫描原理的优化扫描仪的设计。

DESCRIPTION (provided by applicant): Present computed tomography systems provide limited temporal resolution. Large spatial coverage requires sequential acquisition of slices as the patient table passes through a narrow region of exposure. This is true for helical CT scanners as well as electron beam CT (EBCT). There are several consequences of this. For contrast enhanced angiographic studies or studies of tumor contrast uptake, there is little dynamic information available at any anatomical location and the timing of the acquisition relative to the contrast arrival can be variable from patient to patient. For coronary artery imaging the need to acquire substantial sectors of angular data during the acquisition of each slice as the table moves past the source leads to coronary artery motion during acquisition times on the order of fifty milliseconds, even when EBCT is used. Failure to properly advance the sector in sequential heartbeats can lead to inadequate angular sampling and technically unacceptable examinations. Recently, several groups have begun to investigate volume CT systems using conventional x-ray tubes rotated in a single circular path with an opposed flat panel X-ray detector in conjunction with table motion. Although this increases the useful detection solid angle it does not provide optimal source trajectories for dynamic imaging over large fields of view. We propose to investigate the feasibility of an advanced CT system in which the x-ray focal spot is rapidly varied along the length (Z dimension) of the patient during gantry rotation (Z-Scan). This will be accomplished by means of a scanning electron beam or a linear array of discrete focal spots producing a flexible distribution of cone beam sources opposed by large detector arrays. Source trajectories can be optimized for particular clinical applications. The availability of arbitrary source trajectories wilt permit large volume dynamic time resolved detection of contrast material dynamics without significant table motion and, for coronary artery imaging, will permit a short exposure times in each cardiac phase. We will investigate the extension to X-ray CT of MRI acquisition schemes that have enabled us to acquire contrast-enhanced MR images with speeds up to a factor of forty faster than with conventional Cartesian MRI. In the R21 phase, the potential performance of systems based on the proposed approach will be studied using simulations. Measurements and image reconstructions wilt be generated using an X-ray test bed in which a conventional source will be moved to simulate the contemplated source trajectories. In the R33 phase a source test bed employing scanned electron beam technology or distributed pulsed sources will be developed. Potential applications of the contemplated scanner include dynamic studies of tumor contrast uptake, time resolved CT angiography, and coronary artery imaging. We will focus on the latter two applications and, based on the proposed studies, will develop a design for an optimized scanner based on the Z-Scan principle.