Non-contrast-enhanced peripheral MR angiography

项目摘要 在外周动脉疾病（PAD）患者中， 对于诊断和治疗计划至关重要。虽然许多血管造影技术 目前，非对比增强（NCE）磁共振血管造影（MRA） 与数字减影相比，由于无创性，被认为是一种非常有前途的方式 血管造影术（DSA），和没有副作用，不像计算机断层扫描（涉及 电离辐射）和钆对比剂增强MRA（涉及肾源性系统性 纤维化）。因此，在过去的几十年中，已经探索了许多NCE MRA方法，但仍然处于 由于血管造影覆盖范围有限等问题， 空间分辨率和长扫描时间（特别是当需要多次采集时）。 该项目将重点关注新的NCE MRA方法，该方法可实现高血管对比度，高空间分辨率， 所有3个维度的分辨率和短扫描时间内的大血管造影覆盖范围。水平为核心 所提出的方法是速度选择性（VS）磁化准备， 通过抑制背景材料同时基于其速度保留动脉血来进行对比。 由于空间非选择性的性质，VS准备可以与具有大分辨率的3D编码组合。 与基于流入的方法不同， 静止间隔单次激发成像（QISS）。此外，VS准备生成阳性血管造影 直接从单次采集中进行对比，而不是需要两次采集的流量敏感方法 收购要减。我们将首先开发VS激励脉冲序列，其对以下各项具有鲁棒性： B 0和B1场的潜在变化，并实现多方向流动灵敏度。调查领域 将包括多个重聚焦脉冲，Malcom-Levitt相位循环和两个- 维VS准备脉冲。利用背景抑制图像的稀疏性， MRA，我们将通过将压缩感知与并行相结合来实现高速率扫描加速 图像重建虽然所提出的VS-MRA适用于不同的血管区域， 该项目将重点关注外周血管造影术作为代表性临床应用。我们将优化 通过选择最佳重聚焦脉冲数和重聚焦类型的VS-MRA脉冲序列 复合脉冲使用优化的协议，最后，诊断性能将在 以PAD患者的X线血管造影作为对照，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.