Expanding magnitude-based MRI relaxometry of human brain by using the complex signal for high resolution concomitant multiparametric and cerebrovascular mapping

磁共振成像(MRI)由于其图像具有显著的对比度，已成为研究大脑结构不可或缺的工具。近年来，大量的图像处理工具已经变得唾手可得，从而极大地增加了研究大脑如何对疾病和/或治疗做出反应的数量。尽管有过多的结果，但这些方法依赖于具有一定随意性的相对信号对比度的定性MR图像，这一事实仍然对观察到的随着疾病/治疗而发生的大脑变化的准确性和解释提出了挑战。虽然定量磁共振成像(QMRI)的目的是捕捉控制MRI信号的固有参数并揭示潜在组织的微观结构信息，但qMRI参数映射的使用并不容易。磁共振指纹图谱(MRF)的出现突显了磁共振学界的认识，即脑的多参数图谱对于揭示观察到的大脑局灶性差异和其他组织微结构变化的生物学基础至关重要。有趣的是，尽管大脑对氧气的需求很高，因此存在着广泛的脑血管，但用于研究大脑结构的MR图像无法区分血管，因此在研究MR结构图像时没有考虑它们的贡献。然而，当使用不同的序列收集数据时，MRI可以用来检测脑血管系统。*我在这里提出的研究计划试图整合扫描序列和获取的数据，以便能够在临床相关的扫描时间内以高分辨率进行人脑的多参数和脑血管成像。这将通过利用复杂的(相位和幅度)磁共振信号并对获取数据的方式进行微小调整来实现。血管系统的描绘将使组织和血管解缠，从而产生一种新的、有效的方法来更好地探测大脑，从而可以揭示在人脑结构磁共振图像中观察到的体积变化/差异的生物来源。此外，通过对水化状态和脑血流的实验操作，我们将测量所产生的多参数地图对微观结构变化的敏感性。这些实验还将能够测量水合作用和脑血流对大脑结构形状和大小的影响，揭示和/或摒弃与结构磁共振中使用的常见技术相关的可能混淆。总而言之，我们将促进我们对疾病/治疗过程中发生的微结构组织和血管变化的理解。

Magnetic Resonance Imaging (MRI) has become an indispensable tool to study brain structures due to the remarkable contrast that can be obtained in MR images. In recent years, numerous image processing tools have become readily available, thus drastically increasing the number of studies that look at how the brain changes in response to disease and/or treatment. Despite the plethora of results, the accuracy and interpretation of observed brain changes with disease/treatment remain challenged by the fact that such approaches rely on qualitative MR images with somewhat arbitrary, relative signal contrast. While quantitative MRI (qMRI) aims to capture inherent parameters that govern the MRI signal and reveal microstructural information about underlying tissue, the use of qMRI parametric mapping is not readily available. The recent advent of MR fingerprinting (MRF) highlights the recognition in the MR community that multiparametric maps of brain are critical for uncovering a biological basis for observed focal brain differences and other changes in tissue microstructure. Interestingly, despite the fact that the brain has a high demand for oxygen, and thus, there is extensive cerebral vasculature, the MR images that are used to study brain structures are not able to distinguish blood vessels and thus their contribution is not considered when studying MR structural images. However, MRI can be used to detect cerebral vasculature when different sequences are used to collect the data.******The research program I am proposing here attempts to consolidate scanning sequences and acquired data to enable concomitant multiparametric and cerebrovascular mapping of human brain at high resolution in a clinically relevant scan time. This will be achieved by exploiting the complex (phase and magnitude) MR signal and making small adjustment to the way the data is acquired. The depiction of vasculature will enable a disentanglement of tissue and blood vessels, resulting in a novel and efficient approach to better probe the brain such that a biological source of volumetric changes/differences observed in structural MR images of the human brain can be uncovered. Furthermore, through experimental manipulations of hydration status and cerebral blood flow, we will be measuring the sensitivity of the multiparametric maps produced, to changes in microstructure. These experiments will also enable measurements of the effects of hydration and cerebral blood flow on the shapes and sizes of brain structures, revealing and/or discarding possible confounds associated with common techniques used in structural MRI. In summary, we will enable the advancement of our understanding of the microstructural tissue and vascular changes that occur with disease/treatment.