Reproducibility of rest and exercise stress contrast-enhanced calf perfusion magnetic resonance imaging in peripheral arterial disease

Background: The purpose was to determine the reproducibility and utility of rest, exercise, and perfusion reserve (PR) measures by contrast-enhanced (CE) calf perfusion magnetic resonance imaging (MRI) of the calf in normal subjects (NL) and patients with peripheral arterial disease (PAD). Methods: Eleven PAD patients with claudication (ankle-brachial index 0.67 +/- 0.14) and 16 age-matched NL underwent symptom-limited CE-MRI using a pedal ergometer. Tissue perfusion and arterial input were measured at rest and peak exercise after injection of 0.1 mM/kg of gadolinium-diethylnetriamine pentaacetic acid (Gd-DTPA). Tissue function (TF) and arterial input function (AIF) measurements were made from the slope of time-intensity curves in muscle and artery, respectively, and normalized to proton density signal to correct for coil inhomogeneity. Perfusion index (PI) = TF/AIF. Perfusion reserve (PR) = exercise TF/rest TF. Intraclass correlation coefficient (ICC) was calculated from 11 NL and 10 PAD with repeated MRI on a different day. Results: Resting TF was low in NL and PAD (mean +/- SD 0.25 +/- 0.18 vs 0.35 +/- 0.71, p = 0.59) but reproducible (ICC 0.76). Exercise TF was higher in NL than PAD (5.5 +/- 3.2 vs. 3.4 +/- 1.6, p = 0.04). Perfusion reserve was similar between groups and highly variable (28.6 +/- 19.8 vs. 42.6 +/- 41.0, p = 0.26). Exercise TF and PI were reproducible measures (ICC 0.63 and 0.60, respectively). Conclusion: Although rest measures are reproducible, they are quite low, do not distinguish NL from PAD, and lead to variability in perfusion reserve measures. Exercise TF and PI are the most reproducible MRI perfusion measures in PAD for use in clinical trials.