Functional Magnetic Resonance Imaging in the Evaluation of the Elastic Properties of Ascending Aortic Aneurysm

Abstract Objective: To evaluate the aortic wall elasticity using the maximal rate of systolic distension (MRSD) and maximal rate of diastolic recoil (MRDR) and their correlation with the aortic size index (ASI). Methods: Forty-eight patients with thoracic aortic aneurysm were enrolled in this study. A standard magnetic resonance imaging (MRI) protocol was used to calculate MRSD and MRDR. Both MRSD and MRDR were expressed as percentile of maximal area/10-3 sec. ASI (maximal aortic diameter/body surface area) was calculated. A correlation between MRSD, MRDR, ASI, and the patient’s age was performed using regression plot. Results: A significant correlation between MRSD (t=-4,36; r2=0.29; P≤0.0001), MRDR (t=3.92; r2=0.25; P=0.0003), and ASI (25±4.33 mm/m2; range 15,48-35,14 mm/m2) is observed. As ASI increases, aortic MRSD and MRDR decrease. Such inverse correlation between MRSD, MRDR, and ASI indicates increased stiffness of the ascending aorta. A significant correlation between the patient’s age and the decrease in MRSD and MRDR is observed. Conclusion: MRSD and MRDR are significantly correlated with ASI and the patient’s age. They seem to describe properly the increasing stiffness of aortas. These two new indexes provide a promising, accessible, and reproducible approach to evaluate the biomechanical property of the aorta.**摘要** **研究目的**：采用收缩期最大扩张速率（maximal rate of systolic distension, MRSD）与舒张期最大回弹速率（maximal rate of diastolic recoil, MRDR）评估主动脉壁弹性，并分析二者与主动脉尺寸指数（aortic size index, ASI）的相关性。 **研究方法**：本研究纳入48例胸主动脉瘤患者。采用标准磁共振成像（magnetic resonance imaging, MRI）方案计算MRSD与MRDR，二者以最大面积的百分值/10⁻³秒表示。计算主动脉尺寸指数（ASI，即主动脉最大直径/体表面积）。采用回归图分析MRSD、MRDR、ASI与患者年龄之间的相关性。 **研究结果**：本研究观察到MRSD（t=-4.36；r²=0.29；P≤0.0001）、MRDR（t=3.92；r²=0.25；P=0.0003）与ASI（25±4.33 mm/m²，范围15.48~35.14 mm/m²）之间存在显著相关性。随着ASI升高，主动脉MRSD与MRDR均降低。MRSD、MRDR与ASI之间的这种负相关提示升主动脉僵硬度升高。此外，患者年龄与MRSD、MRDR的降低存在显著相关性。 **研究结论**：MRSD与MRDR与ASI及患者年龄均存在显著相关性，可准确反映主动脉僵硬度的升高情况。这两项新型指标为评估主动脉生物力学特性提供了一种极具前景、易于实施且可重复的方法。