Noninvasive determination of local wavespeed and distensibility of the femoral artery by comb-excited Fourier velocity-encoded magnetic resonance imaging: Measurements on athletic and nonathletic human subjects

SummaryThe local distensibility of arteries is of interest because distensibility varies from artery to artery, may be altered by disease to different extents in different arteries, and may be modified by physiological or pharmacological means. Using magnetic resonance imaging (MRI) we have measured local arterial wavespeed in the femoral artery in healthy human subjects and calculated local arterial distensibility. We acquired 2-D coronal and sagittal MR phase contrast angiograms of the femoral artery. We used a novel imaging technique, comb-excited Fourier velocity-encoded MRI, to obtain simultaneous measurements of arterial blood velocity at two stations 14cm apart on the femoral artery. The separation of the two stations divided by the delay between the onset of forward flow at the two stations was used to calculate the wavespeed. The measurements were made on 16 healthy men (8 athletes, 8 non-athletes) in the age range 20–30 years, who were scanned with the use of ECG gating and an extremity coil in a 1.5 Tesla scanner (GE Medical Systems, Milwaukee, WI). By systematically altering the delay between the R-wave and data acquisition, a temporal resolution of 2–4ms was achieved. The onset of forward flow at each station was determined from a least-squares fit to the data for 30% of the maximum velocity during the cardiac cycle. Average femoral artery wavespeed was 7.7m/s ± 1.2 in the athletes and 11.5m/s ± 1.1 in the non-athletes (P < 0.001). The corresponding arterial distensibility values were 1.87 ± 0.86 × 10−5kg−1 s2m and 7.72 ± 1.63 × 10−6kg−1 s2m (P < 0.001). In most of the subjects there was transient flow reversal in the femoral artery immediately preceding the onset of forward flow. This helped in the identification of the onset of forward flow and hence the determination of arterial wavespeed.