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

The local distensibility of arteries is of interest because distensibi lity varies from artery to artery, may be altered by disease to differ ent extents in different arteries, and may be modified by physiologica l or pharmacological means. Using magnetic resonance imaging (MRI) we have measured local arterial wavespeed in the femoral artery in health y human subjects and calculated local arterial distensibility. We acqu ired 2-D coronal and sagittal MR phase contrast angiograms of the femo ral artery. We used a novel imaging technique, comb-excited Fourier ve locity-encoded MRI, to obtain simultaneous measurements of arterial bl ood velocity at two stations 14 cm apart on the femoral artery. The se paration 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-athle tes) in the age range 20-30 years, who were scanned with the use of EC G gating and an extremity coil in a 1.5 Tesla scanner (GE Medical Syst ems, Milwaukee, WI). By systematically altering the delay between the R-wave and data acquisition, a temporal resolution of 2-4 ms was achie ved. The onset of forward flow at each station was determined from a l east-squares fit to the data for 30% of the maximum velocity during th e cardiac cycle. Average femoral artery wavespeed was 7.7 m/s +/- 1.2 in the athletes and 11.5 m/s +/- 1.1 in the non-athletes (P < 0.001). The corresponding arterial distensibility values were 1.87 +/- 0.86 X 10(-5) kg-1 s2 M and 7.72 +/- 1.63 x 10(-6) kg-1 s2 m (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 determi nation of arterial wavespeed.