Langham Michael C, Desjardins Benoit, Englund Erin K, Mohler Emile R, Floyd Thomas F, Wehrli Felix W
Departments of Radiology, University of Pennsylvania School of Medicine, 3400 Spruce St. 19104, Philadelphia, PA.
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania.
Acad Radiol. 2016 Apr;23(4):457-67. doi: 10.1016/j.acra.2015.12.015. Epub 2016 Feb 22.
Contrast-enhanced angiographic evaluation by magnetic resonance imaging (MRI) and computed tomography (CT) is the reference standard for assessing peripheral artery disease (PAD). However, because PAD and diabetes often coexist, the prevalence of renal insufficiency is a major challenge to contrast-based angiography. The objective of this work is to describe and demonstrate a new application of three-dimensional double-echo steady-state (3D DESS) as a noncontrast vascular MRI method for evaluating peripheral atherosclerosis at 3 Tesla (3T).
A water-selective 3D DESS pulse sequence was designed to simultaneously collect two steady-state free-precession signals (free induction decay and Echo) yielding "black blood" (BB) and "gray blood" (GB) images. For completeness Bloch equation, simulations were performed to characterize DESS signals of various tissues including blood at different velocities and to assess two healthy subjects for the purpose of pulse sequence optimization. Exploratory studies were performed as an add-on protocol to an existing study involving patients with PAD. To evaluate the method's specificity for detecting calcification, images from select patients were compared against CT angiography.
Simulations agreed qualitatively with in vivo images supporting DESS' potential for generating distinct lumen contrast (GB vs BB). Lesions representing calcium were easily identifiable on the basis of signal void occurring on both image types and were confirmed by CT angiography. Further, BB allowed visualization of stent restenosis, and data suggest its ability to visualize acute thrombus by virtue of T2 weighting.
Preliminary investigation and results suggest noncontrast 3D DESS to have the potential to improve diagnosis of PAD patients by providing detailed structural assessment of vessel-wall architecture.
磁共振成像（MRI）和计算机断层扫描（CT）增强血管造影评估是评估外周动脉疾病（PAD）的参考标准。然而，由于PAD和糖尿病常同时存在，肾功能不全的患病率是基于对比剂的血管造影的一大挑战。本研究的目的是描述并展示三维双回波稳态（3D DESS）作为一种非对比剂血管MRI方法在3特斯拉（3T）场强下评估外周动脉粥样硬化的新应用。
设计了一种水选择性3D DESS脉冲序列，用于同时采集两个稳态自由进动信号（自由感应衰减和回波），生成“黑血”（BB）和“灰血”（GB）图像。为完善布洛赫方程，进行了模拟以表征包括不同流速血液在内的各种组织的DESS信号，并评估两名健康受试者以优化脉冲序列。作为现有一项涉及PAD患者研究的附加方案进行了探索性研究。为评估该方法检测钙化的特异性，将部分患者的图像与CT血管造影进行了比较。
模拟结果与体内图像定性相符，支持DESS产生不同管腔对比（GB与BB）的潜力。基于两种图像类型上出现的信号缺失，代表钙化的病变易于识别，并经CT血管造影证实。此外，BB能显示支架再狭窄，数据表明其凭借T2加权有显示急性血栓的能力。
初步研究及结果表明，非对比剂3D DESS有潜力通过提供血管壁结构的详细评估来改善PAD患者的诊断。
