Calf muscle perfusion at peak exercise in peripheral arterial disease: Measurement by first-pass contrast-enhanced magnetic resonance imaging

Purpose: To develop a contrast-enhanced magnetic resonance (MR) technique to measure skeletal muscle perfusion in peripheral arterial disease (PAD). Materials and Methods: A total of 11 patients (age = 61 +/- 11 years) with mild to moderate symptomatic PAD (ankle-brachial index [ABI] = 0.75 +/- 0.08) and 22 normals were studied using MR-campatible ergometer. PAD and normal(max) (NImax; N = 11) exercised to exhaustion. NIlow (N = 11) exercised to the same workload achieved by PAD. At peak exercise, 0.1 mm/kg of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was infused at 3-4 cm(3)/second followed by a saline flush at the same rate. A dual-contrast gradient echo (GRE) sequence enabled simultaneous acquisition of muscle perfusion and arterial input function (AIF). The perfusion index (PI) was defined as the slope of the time-intensity curve (TIC) in muscle divided by the arterial TIC slope. Results: Median workload was 120 Joules in PAD, 210 Joules in NIlow, and 698 Joules in NImax (P < 0.001 vs. NIlow and PAD). Median PI was 0.29 in PAD (25th and 75th percentiles [%] = 0.20, 0.40), 0.48 in NIlow (25th, 75th % = 0.36. 0.62; P < 0.02 vs. PAD), and 0.69 in NIlow (25th, 75th % = 0.5. 0.77; P < 0.001 vs. PAD). Area under the ROC-curve for PI differentiating patients from NImax was 0.95 (95% confidence interval [CI] = 0.77-0.99). Conclusion: Peak-exercise measurement of lower limb perfusion with dual-contrast, first-pass MR distinguishes PAD from normals. This method may be useful in the study of novel therapies for PAD.