Dynamic bowtie attenuator for CT dose reduction and dynamic range control

描述(申请人提供)：计算机断层扫描(CT)已成为诊断成像的支柱。CT的高利用率导致了更多的使用，因此，人们对个人和人口的辐射负担感到担忧。虽然已经开发了许多技术来减少CT的剂量，但进一步减少是可能的，也是谨慎的，ALARA原则规定，任何合理可实现的减少都应该采用。众所周知，通过使用患者前衰减器(“蝴蝶结”滤光器)来控制入射辐射分布，可以在给定的图像质量水平下减少患者剂量，并且还可以减少动态范围要求和散射的影响。然而，系统最多只有几个衰减器形状可供选择，并且滤光片在扫描期间是固定的。充其量，它们最适合圆形对称的圆柱体对象。相比之下，患者的衰减特性相当不规则。在以前的研究中，我们表明动态控制照明轮廓可以显著减少剂量，但这项工作假设使用复杂且昂贵的源阵列。相比之下，动态衰减器将是在照明轮廓中实现类似控制的经济高效的解决方案。这种动态衰减器将为每个患者、切片位置、观察方向和临床应用量身定做辐射分布。这与个性化医疗的努力是一致的。关键的要求是衰减器需要具有很强的适应性，并且还需要提供平稳的通量变化。以前的设计都不够好。我们开发了一种满足调制要求的设计概念，通过使用具有沿轴向变化的三角形横截面的可移动楔形衰减器来产生分段的线性动态轮廓。最初的计算机模拟预测了探测器上X射线信号的剂量和动态范围的大幅减少。剂量的减少将带来立竿见影的好处，而动态范围的减少将使更早采用具有额外好处的光子计数探测器。与源阵列方法相比，动态蝴蝶结与传统的CT系统设计兼容，因此如果可行，它可以很容易地转化为临床使用。在拟议的研究中，w将进行全面的计算机模拟以优化设计并预测性能优势，构建动态衰减器阵列的一部分，并进行实验以验证这一概念。一旦这项研究完成，动态蝴蝶结的概念将准备好进入商业系统。

DESCRIPTION (provided by applicant): Computed Tomography (CT) has become a mainstay in diagnostic imaging. The high utility of CT has led to increased use and, as a result, to concerns about the radiation burden to individuals and the population. Although many technologies have been developed to reduce the dose from CT, further reductions are both possible and prudent, and the ALARA principle dictates that any reduction that is reasonably achievable should be adopted. Control of the incident radiation profile through the use of a pre-patient attenuator ("bowtie" filter) is known to reduce patient dose for a given level of image quality and also to reduce the dynamic range requirements and the effects of scatter. However, systems have at most a few attenuator shape choices and the filter is fixed during the scan. At best, they are optimal for circularly symmetric cylindrical objects. By contrast, patients' attenuation properties are rather irregular. In previous research we showed that dynamic control of the illumination profile can lead to significant dose reduction, but that work assumed the use of complex and expensive source arrays. By contrast, a dynamic attenuator would be a cost effective solution for achieving similar control in the illumination profile. Such a dynamic attenuator would tailor the radiation distribution for each patient, slice location, viewing directon, and clinical application. This is aligned with efforts toward personalized medicine. The key requirement is that the attenuator needs to be very adaptive and also provide smooth variation in flux. Prior designs fall short. We have developed a design concept that meets the modulation requirements by using movable wedge attenuators with triangular cross-sections that vary in the axial direction to produce piece-wise linear, dynamic profiles. Initial computer simulations predic large reductions in dose and in the dynamic range of the x-ray signal at the detector. The dose reduction would be of immediate benefit while the reduction in dynamic range would enable the earlier adoption of photon-counting detectors that would have additional benefits. In contrast to the source array approach, the dynamic bowtie is compatible with conventional CT system designs, so if viable it could be readily translated into clinical use. In the proposed research, w will conduct thorough computer simulations to optimize the design and predict performance benefits, build a portion of a dynamic attenuator array, and conduct experiments to validate the concept. Once this research is complete, the dynamic bowtie concept would be ready for adoption into commercial systems.