Wilson John S, Zhong Xiaodong, Hair Jackson, Robert Taylor W, Oshinski John N
Department of Radiology and Imaging Sciences,Emory University School of Medicine,Atlanta, GA 30322e-mail:
Magnetic Resonance R&D Collaborations,Siemens Healthcare,Atlanta, GA 30322.
J Biomech Eng. 2019 Jun 1;141(6):0609011-06090111. doi: 10.1115/1.4040910.
Regional tissue mechanics play a fundamental role in the patient-specific function and remodeling of the cardiovascular system. Nevertheless, regional in vivo assessments of aortic kinematics remain lacking due to the challenge of imaging the thin aortic wall. Herein, we present a novel application of displacement encoding with stimulated echoes (DENSE) magnetic resonance imaging (MRI) to quantify the regional displacement and circumferential Green strain of the thoracic and abdominal aorta. Two-dimensional (2D) spiral cine DENSE and steady-state free procession (SSFP) cine images were acquired at 3T at either the infrarenal abdominal aorta (IAA), descending thoracic aorta (DTA), or distal aortic arch (DAA) in a pilot study of six healthy volunteers (22-59 y.o., 4 females). DENSE data were processed with multiple custom noise reduction techniques including time-smoothing, displacement vector smoothing, sectorized spatial smoothing, and reference point averaging to calculate circumferential Green strain across 16 equispaced sectors around the aorta. Each volunteer was scanned twice to evaluate interstudy repeatability. Circumferential Green strain was heterogeneously distributed in all volunteers and locations. The mean spatial heterogeneity index (standard deviation of all sector values divided by the mean strain) was 0.37 in the IAA, 0.28 in the DTA, and 0.59 in the DAA. Mean (homogenized) peak strain by DENSE for each cross section was consistent with the homogenized linearized strain estimated from SSFP cine. The mean difference in peak strain across all sectors following repeat imaging was -0.1±2.3%, with a mean absolute difference of 1.7%. Aortic cine DENSE MRI is a viable noninvasive technique for quantifying heterogeneous regional aortic wall strain and has significant potential to improve patient-specific clinical assessments of numerous aortopathies, as well as to provide the lacking spatiotemporal data required to refine patient-specific computational models of aortic growth and remodeling.
局部组织力学在心血管系统的个体功能和重塑中起着基础性作用。然而，由于对薄主动脉壁成像存在挑战，主动脉运动学的局部体内评估仍然缺乏。在此，我们展示了一种利用刺激回波位移编码（DENSE）磁共振成像（MRI）来量化胸主动脉和腹主动脉的局部位移和圆周格林应变的新应用。在一项针对6名健康志愿者（年龄22 - 59岁，4名女性）的初步研究中，于3T场强下在肾下腹主动脉（IAA）、胸降主动脉（DTA）或主动脉弓远端（DAA）采集二维（2D）螺旋电影DENSE和稳态自由进动（SSFP）电影图像。使用多种定制降噪技术处理DENSE数据，包括时间平滑、位移矢量平滑、扇形空间平滑和参考点平均，以计算主动脉周围16个等间距扇形区域的圆周格林应变。每位志愿者扫描两次以评估研究间的可重复性。圆周格林应变在所有志愿者和部位均呈异质性分布。IAA的平均空间异质性指数（所有扇形区域值的标准差除以平均应变）为0.37，DTA为0.28，DAA为0.59。DENSE测量的每个横截面的平均（均匀化）峰值应变与从SSFP电影估计的均匀化线性应变一致。重复成像后所有扇形区域的峰值应变平均差异为 -0.1±2.3%，平均绝对差异为1.7%。主动脉电影DENSE MRI是一种可行的无创技术，可用于量化主动脉壁异质性局部应变，在改善多种主动脉疾病的个体临床评估方面具有巨大潜力，同时也能提供完善主动脉生长和重塑个体计算模型所需的缺失的时空数据。
