Novel Acquisition Methods for Diffusion MRI

激励-核磁共振固有的生物物理对比度参数之一是质子自扩散，可通过扩散加权成像(DWI)进行测量。扩散张量成像(DTI)是一种非侵入性定量绘制各向异性水扩散图的MRI方法，因此可以对脑白质(WM)的微结构进行无创性研究，这可能有助于诊断和了解脑白质异常和成熟延迟的病理生理机制。DTI还被广泛用于肿瘤患者和非局灶性疾病患者的WM通路的非侵入性追踪。不幸的是，DTI仍然不仅受到生理运动的困扰，而且还面临着随着磁场的增加而增加的严重技术困难；另一方面，磁场越高，信噪比(SNR)就越高。高场运动补偿DTI的主要受益者之一将是儿童，因为他们的头部较小，运动的可能性较高。AIMS-这项为期两年的研究工作的首要目标是改进扩散加权多激发螺旋成像，以在2D和3D扩散张量成像方面产生重大改进。具体地说，该项目侧重于改进螺旋捕获方法和相应的重建技术，以减少失真、提高对运动的免疫力、减少射频沉积并提供更好的空间分辨率。 还特别强调了改善该序列的图像质量的儿科成像。具体目标是：(具体目标1)开发和优化针对2D和3D成像的实时螺旋磁共振扩散加权成像的采集和重建方法；(特定目标2)针对不同的临床应用和不同的运动类型，确定成人和儿童在3T和7T的2D和3D最佳DTI扫描参数。 方法：将在模拟和模型研究中开发和优化导航仪、(前瞻性和回溯性)运动和非共振校正方案以及增强的并行成像重建算法。健康儿童(n=62)和成人(n=30)将参加广泛的测试。对于一系列不同的临床问题和运动变化，最佳的DTI扫描参数将由经验丰富的神经成像师和神经放射科医生决定。原始k空间数据和高分辨率扩散张量数据将被添加到登记处，并可向公众提供，以改进图像重建算法(例如，非共振校正、并行成像、扩散相导航、网格重建)、张量处理(例如，研究部分体积效应、跨越纤维、复杂的轨道追踪算法)，并为成人和儿童提供一个可在未来试验中使用的标准化数据库。 意义-我们相信，在这个项目成功完成后，DTI可以实现显着的改善，这将改善对患有各种病理条件的患者的形态测量评估和轨迹追踪。白质和神经束投影的异常可以为几种攻击白质的疾病的病理生理学提供重要的见解，并进一步了解患有和不患有白质障碍的儿童的特定神经发育轨迹。

MOTIVIATION - One of MRI’s inherent biophysical contrast parameters is proton self-diffusion, which can be measured by diffusion-weighted imaging (DWI). A variant, Diffusion Tensor Imaging (DTI), is an MRI method for noninvasive quantitative mapping of anisotropic water diffusion, thereby allowing the non-invasive investigation of white matter (WM) microstructure which might aid in the diagnosis and understanding the pathophysiology of white matter abnormalities and delayed maturation. DTI has been also used extensively for non-invasive tracing of WM pathways in tumor patients and in patients harboring non-focal disease. Unfortunately, DTI still suffers not only from physiologic motion but also from profound technical difficulties that increase with higher magnetic fields; higher magnetic fields on the other hand would offer substantially more signal-to-noise ratio (SNR). One of the major benefactors from motion-compensated DTI at high field would be children because of their smaller head sizes and the higher likelihood of motion. AIMS - The overarching goal of this 2-year research effort is to improve diffusion-weighted multi-shot spiral imaging to create significant improvements in 2D and 3D diffusion tensor imaging. Specifically, the project focuses on improvements for spiral acquisition methods and corresponding reconstruction techniques that reduce distortions, improve immunity to motion, diminish RF deposition, and provide better spatial resolution. Special emphasis is also given on improving image quality of this sequence for pediatric imaging. The specific aims are: (Specific Aim #1) to develop and optimize acquisition and reconstruction methods for real-time spiral diffusion-weighted MRI for 2D and 3D acquisitions; (Specific Aim #2) to define optimal DTI scan parameters for 2D and 3D for adults and children at 3T and 7T for different clinical applications and variants of motion. METHODS - Navigator, (prospective and retrospective) motion and off-resonance correction schemes in concert with augmented parallel imaging reconstruction algorithms will be developed and optimized both in simulations and phantom studies. Healthy children (n=62) and adults (n=30) will be enrolled for extensive testing. Optimal DTI scan parameters for a battery of different clinical questions and variants of motion will be determined by experienced neuroimagers and neuroradiologists. The raw k-space data and high-resolution diffusion tensor data will be added to a registry and can be made available to the public to improve image reconstruction algorithms (e.g. off-resonance correction, parallel imaging, diffusion phase navigation, gridding reconstruction), tensor processing (e.g. studying partial volume effects, crossing fibers, complex tract tracing algorithms) and to provide a normative database for adults and children that can be used in future trials. SIGNIFICANCE –We believe that upon successful completion of this project significant improvements in DTI can be achieved that will improve morphometric assessment and tract tracing in patients harboring various pathologic conditions. Abnormalities in WM and tract projections could provide crucial insights in the pathophysiology of several diseases that attack white matter, and further the understanding of specific neurodevelopmental trajectories of children with and without WM disorders.