Fast Numerical Modeling Of Medical Ultrasound For Therapy And Imaging

摘要： 医学超声的许多重要发展都是通过大规模超声模拟实现的， 这对于新设备和应用的设计、评估和优化至关重要。尽管这种现象普遍存在， 医学超声的计算机模拟，诊断和治疗超声中的许多问题， 仍然没有解决，更好的数值模型预计将在解决这些问题中发挥关键作用。 问题特别是，现有的冲击模拟软件需要进行重大改进 组织摧毁术换能器产生的波，以促进肝脏、前列腺和大脑的有效非侵入性治疗 肿瘤的需要更好、更有效的模拟软件来改进横波成像 肝纤维化、甲状腺肿瘤和乳腺肿瘤的模拟需要增强的软件工具 超快成像和其他动态超声成像序列。改进的模型和方法 也需要衰减软组织中的瞬态压缩波和剪切波， 用于剪切波成像、超声显微镜、定量超声和超声断层扫描。主要 本提案的目标是创建有价值的新软件资源，这些资源将支持基础设施的新解决方案。 通过完成三个具体目标，解决医学超声领域的问题。在目标1中，我们建议创建新的 使用不连续Galerkin（DG）方法进行组织摧毁术的瞬态非线性全波超声模拟。 与有限差分、有限元素、伪谱和k空间方法不同，间断Galerkin方法 是在高性能计算系统上评估冲击波全波模型的理想选择。这很重要 因为所有现有的用于医学超声的非线性全波建模工具都是基于这些其它的非线性全波建模工具 当试图对用于组织破坏的高度非线性压力场进行建模时，这些方法遇到了很大的困难。 在目标2中，我们提出了创建瞬态全波模拟剪切波与间断伽辽金 方法，它具有类似的优点时，应用到模拟的剪切波。我们还将讨论另一个 通过用分数阶导数增强所提出的剪切波模拟来限制当前剪切波模拟 描述剪切波在软组织中的衰减和色散的微积分模型。在目标3中，我们建议 为图形处理单元和计算集群创建新的程序，进一步加速所有 FOCUS中的现有程序，“快速面向对象的C++超声模拟器”，以促进有效的 超快成像和其他超声成像序列的数值建模。Aim 3还将整合 FOCUS中的一种新的数值技术，该技术模拟了由几个 为医学超声开发了不同的时间分数和空间分数模型。总的来说，我们预计 所提出的努力产生的模拟软件有很大的潜力，以实现立即和 对整个医疗超声领域的长期影响，特别是在组织破坏、剪切 波弹性成像和其他治疗和诊断超声应用。

Abstract: Many important developments in medical ultrasound are enabled by large-scale ultrasound simulations, which are essential for the design, evaluation, and optimization of new devices and applications. Despite the pervasiveness of computer simulations in medical ultrasound, numerous problems in diagnostic and therapeutic ultrasound remain unsolved, where better numerical models are expected to play a crucial role in the solution to these problems. In particular, significant improvements are needed in the available software for simulations of shock waves produced by histotripsy transducers to facilitate effective noninvasive treatments of liver, prostate, and brain tumors. Better, more effective simulation software is required to enable improvements in shear wave imaging of liver fibrosis, thyroid tumors, and breast tumors, and enhanced software tools are needed for simulations of ultrafast imaging and of other dynamic ultrasound imaging sequences. Improved models and methods are also needed for the attenuation of transient compressional and shear waves in soft tissues, which is significant for shear wave imaging, ultrasound microscopy, quantitative ultrasound, and ultrasound tomography. The main goal of this proposal is to create valuable new software resources that will enable new solutions of fundamental problems in medical ultrasound through the completion of three specific aims. In Aim 1, we propose to create new transient nonlinear full-wave ultrasound simulations for histotripsy using the discontinuous Galerkin (DG) method. Unlike finite difference, finite element, pseudo-spectral, and k-space methods, the discontinuous Galerkin method is ideal for full-wave models of shock waves evaluated on high performance computing systems. This is important because all of the existing nonlinear full-wave modeling tools for medical ultrasound that are based on these other methods encounter significant difficulties when attempting to model highly nonlinear pressure fields for histotripsy. In Aim 2, we propose to create transient full-wave simulations of shear waves with the discontinuous Galerkin method, which has similar advantages when applied to simulations of shear waves. We will also address another limitation of present shear wave simulations by augmenting the proposed shear wave simulations with a fractional calculus model that describes the attenuation and dispersion of shear waves in soft tissue. In Aim 3, we propose to create new programs for graphics processing units and compute clusters that further accelerate all of the existing programs in FOCUS, the `Fast Object-oriented C++ Ultrasound Simulator,' in order to facilitate effective numerical modeling of ultrafast imaging and other ultrasound imaging sequences. Aim 3 will also integrate a new numerical technique into FOCUS that models the power law attenuation and dispersion described by several different time-fractional and space-fractional models developed for medical ultrasound. Overall, we anticipate that the simulation software produced by the proposed effort has great potential to achieve both immediate and long-term impact across the entire field of medical ultrasound, particularly for applications of histotripsy, shear wave elasticity imaging, and other therapeutic and diagnostic ultrasound applications.