High resolution Ultrasound Transmission Tomography

本提案的目的是提供一种新的早期乳腺癌诊断方法：高分辨率三维超声透射断层扫描。通过成像定量组织参数声速和衰减，它使乳腺癌诊断的新见解。目前标准的透射层析成像图像重建使用基于射线的代数重建方法，这极大地限制了分辨率。这限制了该方法的适用性，因为不可能检测小肿瘤。在本项目中，我们通过一种新的迭代重建方法克服了这些局限性，该方法基于更精确的近轴近似正演建模。更高的计算需求由最新和最复杂的优化策略来解决。目标是在求解病态逆问题的迭代次数比现有方法减少一个数量级的同时，将分辨率提高一个数量级。迭代的减少以及在并行基础设施（如多gpu系统）上的高效实现允许在临床相关时间内重建高分辨率三维体，以便在同一天进行诊断。高分辨率透射断层扫描技术的发展对超声在医学中的应用至关重要。所开发的方法将在本项目中应用于一种创新的新成像模式，即用于早期乳腺癌诊断的“3D超声计算机断层扫描”（USCT）。在之前的工作中，卡尔斯鲁厄理工学院（KIT）开发、制造并表征了世界上第一台3D USCT。目前基于射线的三维USCT透射层析成像重建方法的分辨率被限制在最大。12毫米。建立新的重建方法，分辨率提高一个数量级，可能使3D USCT检测到5mm以下的癌症，这大大增加了相关患者的生存机会。通过结合超声系统开发（KIT）和不适定逆问题（海德堡大学）的专业知识，我们准备解决这一研究问题。所开发的方法将通过模拟、模拟和体内数据进行评估。这为后续临床研究评价该方法的敏感性和特异性奠定了基础。建立高分辨率透射层析成像重建将是一个重大突破。它有可能使3D USCT成为一种非常理想和经济的方式，用于澄清可疑的诊断，或者在未来，甚至作为早期乳腺癌检测的筛查方式。

The aim of this proposal is to provide a new method for early breast cancer diagnosis: high resolution three-dimensional ultrasound transmission tomography. By imaging the quantitative tissue parameters sound speed and attenuation, it enables new insights in breast cancer diagnosis. The current standard image reconstruction for transmission tomography uses a ray-based algebraic reconstruction approach, which limits the resolution considerably. This restricts the applicability of the method as the detection of small tumors is not possible. In this project, we overcome these limitations by a new iterative reconstruction method based on a more accurate forward modeling with the paraxial approximation. The substantially higher computational demand is tackled by most recent and sophisticated optimization strategies. The objective is to reach one order of magnitude higher resolution while reducing the number of iterations to solve the ill-posed inverse problem by one order of magnitude compared to the current methods. The reduction of iterations together with an efficient implementation on parallel infrastructures like a multi-GPU system allows the reconstruction of high resolution three-dimensional volumes in a clinically relevant time for diagnosis at the same day. The development of a high resolution transmission tomography method is essential for ultrasound applications in medicine. The developed method will be applied in this project to an innovative new imaging modality, "3D Ultrasound Computer Tomography" (USCT) for early breast cancer diagnosis. In previous work, the Karlsruhe Institute of Technology (KIT) developed, built and characterized the world's first 3D USCT. With the current ray-based reconstruction method, the resolution of transmission tomography in 3D USCT is limited to max. 12mm. Establishing the new reconstruction method, the resolution increase of an order of magnitude potentially allows 3D USCT to detect cancers of a size below 5mm, which increases the chance of survival for concerned patients dramatically. By combining the expertise in ultrasound system development (KIT) and ill-posed inverse problems (University Heidelberg) we are prepared to address this research problem. The developed method will be evaluated by simulated, phantom and in-vivo data. This lays the foundation for following clinical studies to evaluate the sensitivity and specificity of the method. Establishing the high resolution transmission tomography reconstruction would present a major breakthrough. It potentially makes 3D USCT a highly desirable and economic modality for clarification of suspicious diagnoses or - in future - even as screening modality for early breast cancer detection.