Using magnetic resonance imaging measurements for the determination of local wave speed and arrival time of reflected waves in human ascending aorta

Wave speed is one of the key factors describing wave propagation in arteries [1]. Local wave speed is directly related to the arterial wall properties [2]. With aging, arterial wave speed increases due to the stiffening of arterial wall, and also related to arterial disease. Several methods have been proposed to obtain wave speed in arteries, such as foot-to-foot and PU-loop methods. A technique developed recently, lnDU-loop, is a new method to determine local wave speed noninvasively [3]. The theoretical foundation of this method is 1-D conservation of mass and momentum equations for flow in arteries. In this paper, we use the lnDU-loop method to determine the local wave speed in the human ascending aorta. 162 subjects aged 18-79 years, were all free of cardiovascular disease and medication. Cine phase contrast magnetic resonance imaging (CPC-MRI) was performed at segment of ascending aorta. Mean velocity and area change of ascending aorta were recorded with ECG simultaneously. Data were analyzed off line with lnDU-loop to determine local wave speed and arrival time of reflected waves. Wave speed determined by lnDU-loop is 5.20±1.22 m/s; arrival time of reflected waves is 0.050±0.018 s. There are no significant differences between men and women. Also age-related variation of wave speed accorded to the wave speed increases with the increase of age, arrival time of reflected waves decreases with increase of age. This work confirms that lnDU-loop is easy, convenient to use clinically.