BACKGROUND MRI assessment of aortic pulse wave velocity (PWV) helps predict the risk of vascular events, but the recommended phase contrast sampling rate is faster than what is utilized in most clinical sequences. There are many existing MRI databases obtained for assessment of cardiac output using lower temporal frequency sampling where information might be obtained about aortic stiffness (PWV). In this work, we sought to evaluate whether the Group Delay (GD) method can generate a reproducible measure of stiffness and describe expected age-related stiffening of the aortic arch using lower sampling rates in standard clinical sequences. METHODS Phase contrast (PC) MRI was obtained on the ascending and descending aortic arch in a heterogeneous adult cohort (n = 23; 9 women) spanning over a wide range of ages (ages 24-89, mean 49.4 ± 18.4). Data was collected with standard cardiac MRI protocols for cardiac output evaluation (repetition time = 7.8 ms, views-per-segment = 4, encoding velocity = 200 cm/s). Pulse wave transit times (TT) were computed using the GD method, two other validated automated approaches (cross correlation TT Algorithm by Gaddum and Segment by Medviso), and the manual tangent method. Pressure waveforms from tonometry and flow waveforms from PC MRI were used to assess wave reflections. RESULTS Group Delay and TT-Algorithm showed significant and high retest reproducibility (r = 0.86 for both) as well as high PWV correlation with age (r = 0.93, P-value < 0.00005 and r = 0.96, P-value < 0.00005 respectively) and with each other (r = 0.94, P-value < 0.00001, RMSE = 0.94 m/s). Arbitrary altering of the image acquisition trigger in the GD method introduced error of 10%-13%, but the TT-algorithm error range was 11%-25%. CONCLUSION Group Delay enables reproducible assessment of transit time to derive PWV from low temporal resolution clinical cardiac MRI sequences that can also identify age-related stiffening.

中文翻译：

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具有低时间分辨率的临床协议中的MRI主动脉脉搏波速度测量的群时延方法：在异类队列中的验证。

背景技术主动脉脉搏波速度（PWV）的MRI评估有助于预测血管事件的风险，但是推荐的相衬采样率比大多数临床序列所采用的采样率要快。已经获得了许多现有的MRI数据库，这些数据库使用较低的时间频率采样获得了用于评估心输出量的信息，其中可能会获得有关主动脉僵硬度（PWV）的信息。在这项工作中，我们试图评估群延迟（GD）方法是否可以生成可重复的刚度测量值，并使用标准临床序列中的较低采样率描述预期的与年龄相关的主动脉弓刚度。方法在年龄范围广泛（24至89岁，平均49.4±18.4）的异类成年队列（n = 23； 9名妇女）中，在升主动脉弓和降主动脉弓上获得相衬（PC）MRI。使用标准心脏MRI协议收集数据以评估心输出量（重复时间= 7.8毫秒，每段观看次数= 4，编码速度= 200 cm / s）。使用GD方法，其他两种经过验证的自动化方法（Gaddum的互相关TT算法和Medviso的Segment）计算脉搏波传播时间（TT），以及手动切线法。眼压计的压力波形和PC MRI的流量波形用于评估波反射。结果群体延迟和TT算法显示出显着且较高的重测重现性（两者均r = 0.86）以及与年龄的高PWV相关性（r = 0.93，P值<0.00005和r = 0.96，P值<0.00005）彼此之间（r = 0.94，P值<0.00001，RMSE = 0.94 m / s）。GD方法中任意更改图像采集触发器会引入10％-13％的误差，但TT算法的误差范围是11％-25％。结论群时延可对转运时间进行可重复的评估，以从低时间分辨率的临床心脏MRI序列得出PWV，该序列还可识别与年龄有关的僵硬。