Non-Contrast-Enhanced Peripheral MR Angiography

描述（由申请人提供）：下肢外周动脉疾病（PAD）是美国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%。钆增强磁共振血管造影（MRA）已成为一种高度准确、侵入性较小的方法，在许多诊断环境中已取代DSA。最近，钆的使用与肾功能不全患者肾源性系统性纤维化（NSF）的发展有关。不需要钆造影剂的MRA技术的发展对于8% - 38%伴有肾功能不全的PAD患者至关重要。一种很有前途的非对比MRA技术，ECG-FSE，使用ecg触发的3D快速自旋回波序列，利用心脏周期中动脉和静脉流量的差异。根据ECG-FSE的初步经验，我们确定了影响临床患者约50%的图像质量的关键因素：(a)尽管血流特征不同，但对两条腿应用单一的成像参数；(b)相对较长的FSE采集窗口，这会导致图像伪影。在本提案中，我们描述了一种新的方法，VFA-FSE，它结合了一系列技术改进，包括使用可变翻转角度FSE，平行成像和每条腿的单独矢状面采集来克服这些局限性。我们的目标是：(1)系统地开发、测试和完善周围血管3D VFA-FSE MRA，使用脉动血流模型和人类受试者；(2)开发和测试动态4D VFA-FSE成像，包括可变触发延迟和可变血流破坏，以改善血管内评估；(3)在200名PAD患者中前瞻性地测试优化的3站VFA-FSE方案，其中包括血管内4D VFA-FSE。并证明了与弹丸追踪、Gd-MRA和个体时间分辨Gd-MRA相当的准确性。我们研究的首要目标是开发和验证一种强大的、无伪影的ecg触发的可变翻转角度FSE外周MRA技术，该技术可以提供准确的解剖和疾病描述，而不会使患者暴露于外源性造影剂及其相关风险。其次，我们建议探索动态四维VFA-FSE采集，以产生类似时间分辨率的MRA图像，并评估其描述血管内复杂血流模式的准确性。公共卫生相关性：考虑到与钆造影剂相关的风险和成本，我们建议的目标是开发一种准确、高效、可靠的非造影剂增强外周MRA技术，该技术具有避免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.