Assessment of the vessel lumen diameter and degree of stenosis in the superficial femoral artery before intervention: comparison of different algorithms.

PURPOSE: To determine which angiography-based algorithm delivers the most precise results in comparison with direct measurements at intravascular ultrasonography (US) and evaluate their influence on the resulting balloon size for treatment. MATERIALS AND METHODS: Thirty patients with untreated superficial femoral artery stenosis underwent digital subtraction angiography (DSA) and intravascular US before intervention. Two experienced radiologists measured twice the native vessel lumen diameter and the degree of stenosis with all algorithms and modalities in a predefined vessel segment that was perceived to be unaffected. On the basis of the measurements of the vessel lumen diameter, a suitable balloon size for treatment of the lesion was calculated. RESULTS: The mean vessel diameter was 5.7 mm for intravascular US, 6.6 mm for caliper calibration, 6.0 mm for calibration of the catheter tip, and 4.7 mm for visual estimation. Selected balloon sizes were 6.0 mm, 7.0 mm, 6.0 mm, and 5.0 mm, respectively. The mean percentage of stenosis was 78.8% for intravascular US, 81.6% for caliper calibration, 79.7% for catheter calibration, and 88.8% for visual estimation. Intermethod correlation was best for intravascular US and calibration of a catheter tip (0.881, P < .0001). CONCLUSIONS: Measurements on DSA equipment calibrated to a catheter tip correlate best with direct intravascular measurements. Visual estimation can lead to underestimation of the true vessel size and overestimation of stenosis.