Diffusion MRI at Ultra High Field

超高场扩散 MRI

• 批准号: RGPIN-2018-05448
• 负责人: Baron, Corey
• 金额: $ 1.75万
• 依托单位: University of Western Ontario
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=679660
• 关键词: Diffusion; MRI; Ultra; Field

Diffusion MRI at Ultra-High Field******Diffusion magnetic resonance imaging (MRI) measures parameters describing water diffusion (i.e. random molecular motion) in tissue. Diffusion is strongly affected by cell membranes, which allows diffusion MRI to non-invasively probe microscopic tissue characteristics. Accordingly, diffusion MRI has provided a unique ability to study changes in the brain that occur during development and in disease. ******The diffusion of water in tissue has a complex dependence on the cellular properties of the tissue. However, conventional diffusion MRI uses a simplified signal model that does not have a direct physiological interpretation. Oscillating gradient spin-echo (OGSE) diffusion MRI extends the experiment to also measure the frequency dependence of diffusion. This can allow the estimation of specific cell properties like size or density, but this method is time consuming and requires high signal strength. ******Diffusion MRI at ultra high fields increases the signal strength; however, diffusion MRI suffers from severe distortions as magnetic field strength is increased. Some progress towards solving this distortion issue has been made, but these methods drastically increase scan time. Accordingly, diffusion MRI at ultra high field strengths is not commonly performed. The objectives of this proposal are to develop methods for distortion-free diffusion MRI at ultra high field (7 Tesla) and time-efficient OGSE diffusion MRI. This work will involve the design of new data sampling schemes and exploitation of data redundancies to reduce distortions and decrease scan times (i.e., "compressed sensing"), and the development of “model-based reconstructions” that model the physics of the MRI acquisition to remove any remaining distortions.******While these methods will be developed at ultra high field, they will be translatable to typical field strengths. Even at these lower field strengths, distortions are problematic in some regions of the brain. Accordingly, this work will open the door to a whole new set of neurological investigations in these regions, both at ultra high field and typical field strengths. In addition, changes in basic diffusion MRI parameters (e.g., “fractional anisotropy”) have been observed in aging, training, and many neurological conditions. While this tells us something has changed in the brain and potentially when it occurred, the answer to what has changed is usually not clear. Quantifiable tissue parameters, like cell size or density, enabled by OGSE can likely improve our basic physiological understanding of these changes, which would lead to improved understanding of the healthy brain and help to inform on possible interventions for neurological conditions.

超高场的扩散MRI ****扩散磁共振成像（MRI）测量了描述组织中水扩散（即随机分子运动）的参数。扩散受细胞膜的强烈影响，该细胞膜允许扩散MRI到非侵入性探针显微组织特征。根据，MRI的差异提供了研究在发育和疾病期间发生大脑变化的独特能力。 *****水在组织中的扩散对组织的细胞特性具有复杂的依赖性。但是，常规扩散MRI使用了没有直接物理解释的简化信号模型。振荡梯度自旋回波（OGSE）扩散MRI扩展了实验，还测量了扩散的频率依赖性。这可以允许估计特定的单元特性（例如大小或密度），但是此方法耗时，需要高信号强度。 ****超高场处的扩散MRI提高了信号强度。但是，随着磁场强度的增加，MRI的差异遭受严重扭曲。已经提出了解决这个失真问题的一些进展，但是这些方法大大增加了扫描时间。彼此之间，通常没有执行超高场强度下的MRI。该提案的目标是开发在超高场（7 Tesla）和时间效率的OGSE扩散MRI处的无失真扩散MRI的方法。这项工作将涉及新数据抽样方案的设计和数据冗余的开发，以减少扭曲和减少扫描时间（即“压缩敏感性”），并开发“基于模型的重建”，以模拟MRI获取的物理原理，以消除这些方法的静止变形。即使在这些较低的场优势下，在大脑的某些区域中，扭曲也存在问题。根据这项工作，在超高场和典型的野外强度下，这些地区将为这些地区进行全新的神经系统调查打开大门。此外，在衰老，训练和许多神经系统条件下，已经观察到基本扩散MRI参数的变化（例如，“分数各向异性”）。尽管这告诉我们大脑的某些事情发生了变化，并且可能发生时可能发生了变化，但对发生变化的答案通常不清楚。 OGSE启用的可量化组织参数（例如细胞大小或密度）可能会改善我们对这些变化的基本理解，从而改善对健康大脑的理解，并有助于告知神经系统状况的可能干预措施。