Advanced Techniques for Rapid and Artifact-Resistant MR Diffusion Imaging

描述（由申请人提供）：在过去的十年中，MR扩散成像已经发展成为评估中风，组织纤维结构和特征组织水扩散的非常有用的工具。然而，与其他常用的MR图像对比度相比，最先进的MR扩散成像显示出显着的缺陷。目前广泛应用的二维单发扩散成像技术往往产生的图像质量较差，图像几何形状失真，信噪比较差。特别是，扭曲的图像几何形状排除了与不同对比度或不同成像方式的图像的直接比较。为了寻求更好的MR扩散成像脉冲序列，已经提出了许多方法，如缩小视场成像、线和板扫描扩散成像（LSDI和SSDI）、单次平行扩散成像和分段多次扩散成像。虽然所有这些方法都在一定程度上减少了扩散图像中经常出现的过度失真，但这种改进总是以增加扫描时间和/或降低信噪比为代价。在目前的工作中，主要的动机是通过将图像采集扩展到三维来大大缓解信噪比问题。到目前为止，这种扩展到3D一直受阻于长时间的扫描时间和倾向的运动文物。本研究提出的新方法有望克服这些缺点。具体目标是：1)为通常较慢但非常抗伪像的LSDI和SSDI序列开发三维信噪比中性并行化。2)沿三维平行化多镜头分割二维图像，利用三维导航仪校正运动相关相位误差，实现三维扩散成像。3)开发新的加速方案，使3D扩散成像扫描时间保持在实际限制内，同时减少畸变伪影。4)在幻影、正常志愿者和神经上皮肿瘤患者中测试这些进展，这些患者接受临床扫描以制定手术治疗计划。

DESCRIPTION (provided by applicant): Over the last decade MR diffusion imaging has evolved into an immensely useful tool to assess stroke, tissue fiber architecture, and characteristic tissue water diffusion. Nevertheless, compared with other commonly applied MR image contrasts, state-of-the art MR diffusion imaging exhibits significant deficiencies. The widely used 2D single-shot diffusion imaging techniques tend to produce images of inferior quality, often suffering from distorted image geometry and poor signal-to-noise ratio (SNR). In particular, distorted image geometries preclude direct comparisons with images of different contrast or different imaging modalities. In the quest for better MR diffusion imaging pulse sequences, numerous approaches have been suggested, like reduced field-of-view imaging, line and slab scan diffusion imaging (LSDI and SSDI), single-shot parallel diffusion imaging, and segmented multi-shot diffusion imaging. While all of these methods reduce to some extent the excessive distortions often present in diffusion images, such improvements invariably come at the expense of increased scan time and/or reduced SNR. In the present work, the main incentive is to greatly alleviate the SNR problem by extending the image acquisition to 3D. Until now, this extension to 3D has been hampered by prolonged scan times and proneness for motion artifacts. The proposed research introduces novel methods, which promise to overcome these disadvantages. The specific aims are: 1) To develop SNR-neutral parallelization in 3D for the typically slower, but very artifact- resistant LSDI and SSDI sequences. 2) To parallelize multi-shot segmented 2D along the third dimension and to develop 3D diffusion imaging with 3D navigator correction of motion-related phase errors. 3) To develop novel acceleration schemes to keep 3D diffusion imaging scan times within practical limits, while also reducing distortion artifacts. 4) To test these developments in phantoms, in normal volunteers, and in neuroepithelial tumor patients, who undergo clinical scans with the purpose of surgical treatment planning. PUBLIC HEALTH RELEVANCE: The capability of magnetic resonance imaging to measure and image molecular diffusion has provided a new source of image contrast and has proven extremely useful in assessing stroke-related damage and the fiber architecture of nerves and muscles. While 3D diffusion imaging would present significant advantages over 2D imaging, it has up to now been impeded by technical problems, such as long acquisition times and motion artifacts. The present application aims at solving these problems, to enable robust and practical 3D diffusion imaging.