Non-Contrast-Enhanced Peripheral MR Angiography

描述(申请人提供)：在美国，下肢外周动脉疾病(PAD)是发病率和死亡率的主要原因，在75岁以上的人群中，估计患病率高达20%。Gd增强磁共振血管成像(MRA)已经成为一种高精度、侵入性较小的方法，在许多诊断环境中已经取代了DSA。最近，Gd的应用与肾功能不全患者的肾源性系统性纤维化(NSF)的发展有关。对于8-38%的肾功能不全的PAD患者来说，开发不需要Gd造影剂的MRA技术是至关重要的。一种很有前途的无对比磁共振血管成像技术，心电快速自旋回波序列，使用了心电触发的3D快速自旋回波序列，该序列利用了心脏周期中动脉和静脉血流的差异。从初步的ECG-FSE经验中，我们确定了约50%的时间影响临床患者图像质量的关键因素：(A)尽管血流特征不同，但对双腿应用了一组单一的成像参数，以及(B)相对较长的FSE采集窗口，这会导致图像伪影。在这个方案中，我们描述了一种新的方法，VFA-FSE，它结合了一系列的技术改进，包括使用可变翻转角度的FSE，平行成像，以及每条腿单独的矢状面采集来克服这些限制。我们的目标是(1)利用脉动血流模体和人体受试者系统地开发、测试和改进外周血管3D VFA-FSE MRA；(2)开发和测试结合可变触发延迟和可变血流干扰的动态4D VFA-FSE成像，以改善基础血管评估；(3)在200例PAD患者中前瞻性地测试优化的3站VFA-FSE与基础4D VFA-FSE相比，并展示与团注和Gd-MRA以及基础时间分辨Gd-MRA相当的准确性。我们研究的总体目标是开发和验证一种用于外周MRA的健壮且无伪影的心电触发可变翻转角FSE技术，该技术可提供准确的解剖和疾病描述，而不会使患者暴露在外源性造影剂及其相关风险中。其次，我们建议探索动态4D VFA-FSE采集，以产生时间分辨的类MRA图像，并评估其对于描述基础血管中复杂的血流模式的准确性。公共卫生相关性：考虑到与Gd造影剂相关的风险和成本，我们的建议的目标是开发一种准确、高效和可靠的非对比剂增强外周MRA技术，具有省去外源性造影剂和降低成本的优点。

DESCRIPTION (provided by applicant): Lower extremity peripheral arterial disease (PAD) is a major cause of morbidity and mortality in the U.S., with an estimated prevalence up to 20% in those over 75 years. Gadolinium-enhanced MR angiography (MRA) has emerged as a highly accurate, less invasive approach that has replaced DSA in many diagnostic settings. Recently, gadolinium administration has been linked to the development of nephrogenic systemic fibrosis (NSF) in patients with renal insufficiency. Development of MRA techniques that do not require gadolinium contrast is vitally important for the 8 - 38% of PAD patients with renal insufficiency. A promising non- contrast MRA technique, ECG-FSE, uses an ECG-triggered 3D fast spin echo sequence, which exploits differences in arterial and venous flow during the cardiac cycle. From preliminary experience with ECG-FSE, we identified key factors that compromise image quality in clinical patients about 50% of the time: (a) application of a single set of imaging parameters to both legs despite differences in flow characteristics and (b) relatively long FSE acquisition windows, which contribute to image artifacts. In this proposal, we describe a new approach, VFA-FSE, which incorporates a series of technical improvements including use of variable flip angle FSE, parallel imaging, and separate sagittal acquisitions for each leg to overcome these limitations. Our aims are (1) To systematically develop, test, and refine peripheral vascular 3D VFA-FSE MRA using pulsatile flow phantoms and human subjects, (2) To develop and test dynamic 4D VFA-FSE imaging that incorporates variable trigger delay and variable flow-spoiling for improved infragenual vessel evaluation and (3) To test prospectively an optimized 3 station VFA-FSE protocol with infragenual 4D VFA-FSE in 200 PAD patients, and to demonstrate comparable accuracy with bolus-chase and Gd-MRA and infragenual time-resolved Gd-MRA. The overarching goals of our research are to develop and validate a robust and artifact-free ECG-triggered variable flip angle FSE technique for peripheral MRA that provides accurate depictions of anatomy and disease without exposing patients to an exogenous contrast agent and its associated risks. Secondarily, we propose to explore dynamic 4D VFA-FSE acquisitions to produce time-resolved-like MRA images, and assess their accuracy for depicting complex flow patterns in infragenual vessels. PUBLIC HEALTH RELEVANCE: Given the risks and costs associated with gadolinium contrast material, the goal of our proposal is to develop a an accurate, efficient, and robust technique for non-contrast-enhanced peripheral MRA with advantages of obviating exogenous contrast material and reducing costs.