MRI method for quantitatively mapping cerebral microbleeds

描述(申请人提供)：这项研究的目标是开发一种定量MRI方法来绘制脑微出血(CMB)中的铁沉积图。对CMB的研究具有重大的科学和临床意义，CMB是从小脑血管渗出的红细胞中渗出的含铁血黄素沉淀物的局灶性病变。CMB已成为治疗中风患者的一个重要问题，尤其是在评估接受抗凝治疗的患者发生破坏性脑出血(ICH)的风险方面。定量测绘CMB中的铁沉积对于分层抗凝治疗的风险非常有价值。目前，T2*加权MRI中的暗区已经被用来通过解释由铁矿床局部磁场的体素内去相效应引起的观察到的信号损失来识别铁的存在。这种低信号取决于体素的大小和方向，可能与其他信号空洞混淆，不能准确定量铁。我们提出了一种新的定量磁化率图(QSM)方法，通过充分利用T2*梯度回波图像数据中的相位和幅度信息，使用MRI生成铁矿的定量图。在磁共振成像中，通常被忽略的位相图像被用来通过麦克斯韦方程产生与磁化率拟合的局部磁场图。幅度图像被用来提取组织结构信息，以便通过最小不一致性与磁化率界面匹配。我们的初步研究表明，这种支持形态的偶极子反演方法对于定量绘制铁化合物浓度是可行的，从而使煤层气的标准化和定量评估成为可能。我们提出的研究包括以下几个具体目标，以开发和应用脑铁图技术。1)优化数据采集，绘制CMB全脑视野图。2)建立了CMB铁矿QSM的稳健重建模型。3)通过组织学对照，验证脑出血和微出血的QSM。4)应用QSM测量华法林治疗的脑出血患者和非脑出血患者的CMB。 公共卫生相关性：这项拟议的研究将利用无创性磁共振成像开发脑微出血中铁沉积的定量易感性图谱，以评估接受华法林治疗的患者脑内出血的风险。迫切需要标准化对脑微出血的MRI评估，脑微出血是高血压患者毁灭性脑出血的已知风险。目前MRI是检测脑微出血的首选方法，但不是定量的。这项研究的成功发展将导致对大脑微出血的标准化评估，并准确评估因心脏问题而接受华法林治疗的患者脑内出血的风险。

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.