Dynamic bowtie attenuator for CT dose reduction and dynamic range control

描述（由申请人提供）：计算机断层扫描（CT）已成为诊断成像的支柱。CT的高度实用性导致了使用的增加，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，但进一步减少剂量是可能的，也是谨慎的，ALARA原则规定，应采用任何合理可实现的减少。已知通过使用患者前衰减器（"蝴蝶结"滤波器）来控制入射辐射轮廓，以针对给定水平的图像质量降低患者剂量，并且还降低动态范围要求和散射效应。然而，系统最多有几个衰减器形状选择，并且滤波器在扫描期间是固定的。最好的情况下，它们对于圆对称的圆柱形物体是最佳的。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，动态控制的照明配置文件可以导致显着的剂量减少，但这项工作假设使用复杂和昂贵的源阵列。相比之下，动态衰减器将是用于实现照明分布中的类似控制的成本有效的解决方案。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定制辐射分布。这与个性化医疗的努力是一致的。关键要求是衰减器需要非常自适应，并且还提供通量的平滑变化。以前的设计都不理想。我们已经开发出一种设计概念，通过使用具有三角形横截面的可移动楔形衰减器来满足调制要求，该三角形横截面在轴向方向上变化以产生分段线性动态轮廓。最初的计算机模拟预测，探测器上的剂量和x射线信号的动态范围会大幅减少。剂量的减少将立即带来好处，而动态范围的减少将使光子计数探测器能够更早地采用，这将带来额外的好处。与源阵列方法相比，动态蝴蝶结与传统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，我们将进行彻底的计算机模拟，以优化设计和预测性能的好处，建立一个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，动态蝴蝶结概念将准备采用到商业系统。

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.