MRI method for quantitatively mapping cerebral microbleeds

描述（由申请人提供）：本研究的目的是开发一种定量MRI方法，用于绘制脑微出血（CMB）中的铁沉积。研究CMB具有重要的科学和临床意义，CMB是从小脑血管泄漏的红细胞中含铁血黄素沉积的局灶性病变。CMB已成为管理卒中患者的重要关注点，特别是用于评估抗凝治疗患者发生毁灭性脑出血（ICH）的风险。CMB中铁沉积的定量绘图对抗凝治疗的风险分层非常有价值。目前，T2 * 加权MRI中的暗区已被用于通过解释由铁沉积物的局部磁场的体素内失相效应引起的观察到的信号损失来识别铁的存在。这种低强度取决于体素大小和方向，可能与其他信号空洞混淆，并且不允许准确定量铁。 我们提出了一种新的定量磁化率映射（QSM）的方法来生成定量映射的铁矿床使用MRI充分利用T2 * 梯度回波图像数据中的相位和幅度信息。在MRI中通常被忽略的相位图像用于生成局部磁场图，以通过麦克斯韦方程与磁化率拟合。幅值图像用于提取组织结构信息，以通过最小不一致性与磁化率界面匹配。如我们的初步研究所示，这种形态学启用偶极反演方法对于定量映射铁化合物浓度是可行的，因此能够对煤层气进行标准化和定量评价。我们提出的研究包括以下具体目标，发展和应用脑铁映射技术。1)优化全脑CMB标测野的数据采集。2)开发CMB铁矿床QSM的稳健重建。3)使用组织学相关性的脑中出血和微出血的EQSM。4)应用QSM测量华法林治疗的ICH和非ICH患者的CMB。 公共卫生相关性：这项拟议的研究将开发一个定量的铁沉积在脑微出血的敏感性映射使用非侵入性MRI评估脑出血的风险与华法林治疗的患者。脑微出血是高血压患者发生毁灭性脑出血的已知危险因素，目前迫切需要对脑微出血的MRI评估进行标准化。目前MRI是检测脑微出血的首选方法，但它不是定量的。这项研究的成功发展将导致脑微出血的标准化评估，并准确评估华法林治疗心脏病患者脑出血的风险。

DESCRIPTION (provided by applicant): The objective of this research is to develop a quantitative MRI method for mapping iron deposits in cerebral microbleeds (CMB). There is significant scientific and clinical interest in studying CMB, which are focal lesions of hemosiderin deposits from red blood cells leaked out of small brain vessels. CMB have become an important concern for managing stroke patients, particularly for assessing the risk of devastating intracerebral hemorrhage (ICH) in patients under anticoagulation. Quantitative mapping of iron deposits in CMB can be very valuable for stratifying risk of anticoagulation therapy. Currently, dark regions in T2* weighted MRI have been used to identify the presence of iron by interpreting the observed signal loss caused by the intravoxel dephasing effect of local magnetic fields of iron deposits. This hypointensity depends on voxel size and orientation, may be confused with other signal voids, and does not allow accurate quantification of iron. We propose a novel quantitative susceptibility mapping (QSM) approach to generate quantitative mapping of iron deposits using MRI by making full use of both phase and magnitude information in the T2* gradient echo image data. The phase image, typically neglected in MRI, is used to generate a local magnetic field map for fitting with susceptibility via the Maxwell equation. The magnitude image is used to extract tissue structure information for matching with susceptibility interfaces via least discordance. This morphology enabled dipole inversion approach is feasible for quantitatively mapping iron compound concentrations, as demonstrated in our preliminary studies, therefore enabling standardized and quantitative evaluation of CBM. Our proposed research consists of the following specific aims for developing and applying brain iron mapping technology. 1) Optimize data acquisition for mapping fields of CMB in the whole brain. 2) Develop a robust reconstruction for QSM of CMB iron deposits. 3) Validate QSM of bleeds and microbleeds in the brain using histological correlation. 4) Apply QSM to measure CMB in warfarin-treated patients with and without ICH. PUBLIC HEALTH RELEVANCE: This proposed research will develop a quantitative susceptibility mapping of iron deposits in cerebral microbleeds using noninvasive MRI for assessing the risk of intracerebral hemorrhage in patient treated with warfarin. There is an urgent need to standardize the MRI evaluation of cerebral microbleeds, a known risk for the devastating intracerebral hemorrhage in hypertensive patients. Currently MRI is the method of choice for the detection of cerebral microbleeds, but it is not quantitative. Successful development of this research would lead to a standardized evaluation of cerebral microbleeds and an accurate assessment of the risk of intracerebral hemorrhage for patients under warfarin treatment for their heart problems.