Non-contrast-enhanced peripheral MR angiography

项目摘要 在外周动脉疾病(PAD)患者中，对感兴趣动脉的清晰描绘是 对诊断和治疗计划至关重要。虽然许多血管造影术是 目前，非对比增强(NCE)磁共振血管成像(MRA)是 由于非侵入性而不是数字减影，被认为是一种非常有前途的模式 血管造影术(DSA)，而且没有副作用，不像计算机断层扫描(涉及 电离辐射)和Gd增强MRA(涉及肾源性全身性风险 纤维化)。因此，在过去的几十年里，已经探索了许多NCE MRA方法，但仍处于 由于血管造影术覆盖范围有限和 空间分辨率和较长的扫描时间(特别是在需要多次采集时)。 该项目将专注于新的NCE MRA方法，实现高血管对比度，高空间 所有3个维度的分辨率和短扫描时间内血管成像覆盖率大。在这个问题的核心 所提出的方法是速度选择性(VS)磁化准备，该方法产生血管造影 通过抑制背景材料，同时根据其速度保存动脉血液进行对比。 由于空间上的非选择性性质，VS准备可以与3D编码相结合 所有三个维度的视场和高空间分辨率都不同于基于流入的方法，例如 静态间隔单次激发成像(QISS)。此外，VS准备可产生阳性的血管造影 与需要两次采集的流量敏感型方法不同，直接通过一次采集形成对比 要减去的收购。我们将首先开发VS激励脉冲序列，该序列对 B0和B1场中的电势变化，并实现多方向流动敏感性。调查范围 将包括合并多个重新聚焦脉冲、马尔科姆-莱维特相位循环和两个- 维度VS制备脉冲。利用VS图像背景抑制的稀疏性 MRA，我们将通过将压缩感知与并行相结合来实现高速扫描加速 影像重建。虽然建议的VS-MRA适用于不同的血管领域，但这 该项目将重点关注具有代表性的临床应用的外周血管造影术。我们将优化 选择最佳重聚焦脉冲数目和重聚焦类型的VS-MRA脉冲序列 复合脉冲。使用优化的协议，最后将评估诊断性能 对PAD患者行X线血管造影，并与CE-MRA和QISS进行比较。

Project Abstract In patients with peripheral arterial disease (PAD), clear delineation of the arteries of interest is essential for diagnosis and treatment planning. While a number of angiography techniques are available nowadays, non-contrast-enhanced (NCE) magnetic resonance angiography (MRA) is considered a highly promising modality due to non-invasiveness as opposed to digital subtraction angiography (DSA), and the absence of side effects unlike computerized tomography (involving ionizing radiation) and gadolinium-contrast-enhanced MRA (involving the risk of nephrogenic systemic fibrosis). As such, many NCE MRA methods have been explored in the past decades, yet are still at some distance from solid clinical acceptance due to issues such as limited angiographic coverage and spatial resolution, and long scan time (particularly when multiple acquisitions are needed). This project will focus on novel NCE MRA methods which achieve high vessel contrast, high spatial resolution in all 3 dimensions and large angiographic coverage in short scan time. At the core of the proposed method is velocity-selective (VS) magnetization preparation which generates angiographic contrast by suppressing background materials while preserving arterial blood based on their velocity. Due to spatially non-selective nature, VS preparation can be combined with 3D encoding with large FOV and high spatial resolution in all three dimensions unlike inflow-based approaches such as quiescent interval single-shot imaging (QISS). Also, VS preparation generates positive angiographic contrast directly from single acquisition, as opposed to flow-sensitive approaches that require two acquisitions to be subtracted. We will first develop VS excitation pulse sequences which are robust to potential variation in B0 and B1 field and enable multi-directional flow sensitivity. Areas of investigation will include incorporation of multiple refocusing pulses, Malcom-Levitt phase cycling, and two- dimensional VS preparation pulses. Exploiting the sparsity of background-suppressed image of VS- MRA, we will achieve high-rate scan acceleration by combining compressed sensing with parallel imaging reconstruction. While the proposed VS-MRA is applicable for diverse vascular territories, this project will focus on peripheral angiography as representative clinical applications. We will optimize VS-MRA pulse sequences by selecting optimal number of refocusing pulses and type of refocusing composite pulse. Using the optimized protocol, lastly, diagnostic performance will be evaluated in PAD patients with x-ray angiography as the reference with comparisons to CE-MRA and QISS.