Non-contrast 4-D Dynamic MRA in Arteriovenous Malformation (AVM)

描述（由申请人提供）：动静脉畸形（AVM）是一种大脑中的先天性血管异常，动脉和静脉之间存在直接连接，使得血液绕过脑组织。AVM的主要表现是颅内出血，发生率高达40-70%，可能导致永久性损伤或死亡。作为检测和评价血管畸形的金标准，常规数字减影血管造影术（DSA）是一种侵入性手术，具有神经系统并发症的风险，以及电离辐射和碘化造影剂的风险。虽然DSA在血管解剖结构的描绘方面具有上级优势，但它不能提供AVM中血流或分流程度的定量评估。现有的MR技术对于量化血管畸形的血流动力学是次优的，并且血管结构的复杂性常常不能充分显示。动脉自旋标记（ASL）是一种无创MRI技术，利用磁标记的血液水作为内源性示踪剂进行灌注测量。由于AVM中动脉和静脉之间的直接分流，标记的血液自旋表现为血管内造影剂，并且可以用于可视化通过AVM的供血动脉、病灶和引流静脉的动态血流。此外，血流动力学参数，如血流量，血容量和平均通过时间可以通过调整标准示踪剂动力学模型进行量化。我们最近开发了这样一种完全无创和定量的4-D时间分辨dMRA技术相结合的ASL与分段电影多相TrueFISP序列。本提案的目标是进一步开发、验证和评价4-D非造影dMRA在评估AVM血管结构和血流动力学方面的临床效用。在目标1中，将对4-D非造影dMRA进行进一步的技术开发和优化，包括采用血管选择性标记实现多团注脉冲和伪连续ASL（pCASL）;采用视图共享的笛卡尔采样;采用k空间加权图像对比度（KWIC）的动态黄金角径向采集;结合并行成像和潜在压缩感知。在目标2中，将通过与相位对比（PC）MRI和pCASL灌注MRI进行比较，验证使用4- D dMRA定量AVM血流量和分流程度的方法。最后，在目标3中，将通过与DSA、飞行时间（TOF）MRA和T2加权MRI的参考标准进行比较，评价所提出的4-D dMRA技术在AVM患者中的临床实用性。此外，将进行重复扫描，以测试4-D dMRA是否能够检测治疗前后通过AVM的血流变化和分流程度。拟议的4-D dMRA有望为定量评估AVM血流动力学的传统DSA和MRA/MRI技术提供替代和补充方法。它不仅可用于评估AVM，而且可用于其他脑血管疾病，如狭窄闭塞性疾病和脑动脉瘤。!

DESCRIPTION (provided by applicant): An arteriovenous malformation (AVM) is a congenital vascular abnormality in the brain with direct connections between arteries and veins such that blood bypasses brain tissue. The primary presentation of AVM is intracranial hemorrhage which occurs in as many as 40-70% of patients and may lead to permanent injury or death. As the gold standard for the detection and evaluation of vascular malformations, conventional digital subtraction angiography (DSA) is an invasive procedure bearing risks of neurological complications, as well as risks of ionizing radiation and iodinated contrast. While superior for th delineation of vascular anatomy, DSA is not capable of providing quantitative assessments of blood flow or degree of shunt in an AVM. Existing MR techniques are suboptimal for quantifying the hemodynamics of vascular malformation, and the complexity of the vascular architecture is often inadequately demonstrated. Arterial spin labeling (ASL) is a noninvasive MRI technique that utilizes magnetically labeled blood water as an endogenous tracer for perfusion measurements. Due to the direct shunt between arteries and veins in AVMs, the labeled blood spins behave as an intravascular contrast agent, and can be utilized for visualizing the dynamic blood flow through feeding arteries, nidus and draining veins of an AVM. Furthermore, hemodynamic parameters such as blood flow, blood volume and mean transit time can be quantified by adapting the standard tracer kinetic model. We have recently developed such an entirely noninvasive and quantitative 4-D time-resolved dMRA technique by combining ASL with a segmented cine multiphase TrueFISP sequence. The goal of the present proposal is to further develop, validate and evaluate the clinical utility of 4-D non-contrast dMRA in assessing both the vascular architecture and hemodynamics of AVMs. In Aim 1, further technical development and optimization of 4-D non-contrast dMRA will be performed, including implementation of multi-bolus pulsed and pseudo-continuous ASL (pCASL) with vessel selective labeling; Cartesian sampling with view sharing; dynamic golden angle radial acquisition with k-space weighted image contrast (KWIC); in conjunction with parallel imaging and potentially compressed sensing. In Aim 2, validation of methods for quantifying blood flow and degree of shunt through AVMs using 4- D dMRA will be carried out by comparison with phase-contrast (PC) MRI and pCASL perfusion MRI. Finally in Aim 3, the clinical utility of the proposed 4-D dMRA technique will be evaluated in AVM patients by comparison with the reference standard of DSA, time-of-flight (TOF) MRA and T2 weighted MRI. Furthermore, repeated scans will be performed to test whether 4-D dMRA is able to detect changes of blood flow and degree of shunt through AVMs pre and post treatments. The proposed 4-D dMRA is expected to provide alternative and complementary approaches for conventional DSA and MRA/MRI techniques in quantitative assessments of hemodynamics in AVMs. It will be useful not only for evaluation of AVMs, but also for other cerebrovascular disorders such as steno-occlusive diseases and cerebral aneurysms. !