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方法来绘制脑微出血（CMB）中的铁沉积。CMB是一种由小脑血管渗出的红细胞引起的含铁血黄素沉积的局灶性病变，对CMB的研究具有重要的科学和临床意义。CMB已成为脑卒中患者管理的重要关注点，特别是用于评估抗凝治疗患者发生破坏性脑出血（ICH）的风险。CMB中铁沉积的定量制图对于抗凝治疗的风险分层是非常有价值的。目前，T2*加权MRI中的暗区已被用于识别铁的存在，通过解释由铁矿局部磁场的体内减相效应引起的观察到的信号损失。这种低密度取决于体素的大小和方向，可能与其他信号空洞混淆，并且不能准确定量铁。我们提出了一种新的定量磁化率作图（QSM）方法，通过充分利用T2*梯度回波图像数据中的相位和震级信息，利用MRI生成铁矿定量作图。在MRI中通常被忽略的相位图像被用来生成局部磁场图，并通过麦克斯韦方程拟合磁化率。利用幅值图像提取组织结构信息，通过最小不一致度与敏感界面匹配。正如我们的初步研究所证明的那样，这种形态支持的偶极子反演方法对于定量绘制铁化合物浓度是可行的，因此可以对煤层气进行标准化和定量评估。我们提出的研究包括以下具体目标，以开发和应用脑铁映射技术。1)优化全脑CMB图谱场的数据采集。2)建立CMB铁矿床QSM的稳健重建方法。3)利用组织学相关性验证脑出血和微出血的QSM。4)应用QSM测定华法林治疗合并脑出血和不合并脑出血患者的CMB。

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.