Spectral analysis of Doppler ultrasound: Its clinical application in lower limb ischaemia

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Abstract
Twenty-nine patients with symptomatic lower limb ischaemia were studied using a continuous wave Doppler ultrasound spectrum analyser. Frequency spectra were recorded from the peripheral arteries to determine the pulsatility index, damping factor and pulse wave transit time, and the results were related to arteriography. In the aortofemoral segment, the pulsatility index at the common femoral artery decreased significantly with increasing stenosis, but the transit time was only prolonged with total occlusion. In the femoropopliteal segment there were significant differences in all parameters between each grade of stenosis. Accurate Doppler and radiological assessments of the calf vessels were possible in only 31 limbs; ultrasound did not enable differentiation between patent and occluded vessels. The pulsatility index at the common femoral artery may be helpful in detecting aortofemoral disease, and accurate assessment of the femoropopliteal segment is possible, but spectral analysis is of no value in assessing the calf vessels.