MRI Mapping of Venous Oxygenation

描述(由申请人提供)：这项工作的总体目标是开发一种基于无创性MRI的方法来绘制氧提取分数(OEF)图。OEF被认为是卒中半暗带(灌流不足但可挽救的脑组织)的更具体的指标，因此对于卒中患者的谨慎决策是重要的。OEF也是了解BOLD功能成像中大脑新陈代谢和对比机制的关键因素。在这项工作中，静脉T2将被用作静脉氧合的替代物，因为这两个量之间存在着密切的关系。最近的研究表明，可以使用头部主要引流静脉的T2测量来测量全脑OEF。我们将开发一种新的方法，它将绘制T2，从而在整个大脑中映射OEF，提供特定于区域的信息。我们的方法由三个模块组成：1)使用一种新的速度选择激励方案来选择性地激发运动的自旋；2)使用流入的动脉血液的反转标记来消除动脉信号；以及3)使用流动补偿多回波或T2准备成像来映射T2。我们已经对每个组件提出了技术改进建议，并将实施、测试和优化这些改进。我们将量化OEF测量中的残差来源，以使该方法的精度得到很好的表征。在这项工作结束时，我们希望拥有一种优化的人脑OEF非侵入性测量方法，为进一步的技术开发和/或翻译研究提供坚实的基础。

DESCRIPTION (provided by applicant): The overall objective of this work is to develop a non-invasive MRI based method for mapping of Oxygen Extraction Fraction (OEF). OEF is thought to be a more specific indicator of penumbra (under perfused but salvageable brain tissue) in stroke than other quantities, and is therefore important for prudent decision-making in the management of stroke patients. OEF is also a key factor in the understanding of cerebral metabolism and contrast mechanisms in BOLD functional imaging. In this work, venous T2 will be used as a surrogate for venous oxygenation, as there is known to be a tight relationship between these two quantities. Recent work has shown that whole-brain measurements of OEF can be made using T2 measurements in the major draining veins of the head. We will develop a new approach that will map T2 and thereby OEF throughout the brain, providing regionally specific information. Our approach is comprised of three modules: 1) selective excitation of moving spins using a novel velocity selective excitation scheme; 2) nulling of arterial signal using inversion tagging of inflowing arterial blood; and 3) mapping of T2 using flow compensated multi-echo, or T2 prepared imaging. We have proposed technical improvements to each of these components, and will implement, test, and optimize these improvements. We will quantify the sources of residual errors in the OEF measurement so that the accuracy of the method is well characterized. At the conclusion of this work, we expect to have an optimized method for non-invasive OEF measurement in the human brain that provides a solid foundation for further technical development and/or translational research.