1Second Department of Internal Medicine, Kagawa Medical School, 2Telecommunications division, Hitachi, Ltd., 3Department of Cardiovascular Sciences,Tokyo Women's Medical College, 4Clinical Laboratory, Kagawa Medical School
We propose a new method for local measurement of the propagation velocity of a pulse wave for the quantitative evaluation of severity of atherosclerosis. This method uses a complex cross-correlation of Doppler signals and, theoretically, has the potential for precise estimation of the propagation time of a pulse wave of less than 1 msec. Doppler signals shifted by blood flow are detected at two adjacent locations on the artery using the simultaneous two-beam pulsed Doppler method, stored in a computer, and then analyzed by cross correlation. Time delay at maximum correlation output gives propagation time of the pulse wave. In an experimental study using a pulsatile-flow circuit model, regardless of sampling distance and flow-velocity profile, there was little fluctuation in calculated pulse wave velocity. Time resolution of this method was estimated at less than 1 msec, which is sufficient accuracy for measurement of local pulse wave velocity over a 5 cm distance. In a study in vivo of healthy volunteers, local pulse wave velocity was faster in the femoral artery (6.4±0.8 m/sec) than in the carotid artery (4.8±0.5 m/sec) and abdominal aorta (4.0±5 m/sec). The average value of local pulse wave velocities in these three sites was almost the same as the aortic pulse wave velocity conventionally measured between the carotid and femoral arteries. Local pulse wave velocity will thus facilitate quantitative estimation of the distribution and severity of atherosclerosis.