Abstract 11374: Reproducibility of Contrast-Enhanced Calf Perfusion MRI Measures in Peripheral Arterial Disease
Background: Contrast-enhanced (CE) calf perfusion MRI at peak exercise (Ex) distinguishes normal subjects from peripheral arterial disease (PAD) patients. Perfusion at rest can now be measured by CE-MRI. It is unclear whether measuring Ex perfusion or Ex/rest perfusion reserve (PR) is more reproducible and whether signal normalization is additive.
Methods: CE-MRI of the calf was performed in 16 age-matched healthy controls (CL) and 7 patients with PAD (ABI 0.67±0.14) before and after plantar-flexion symptom-limited Ex on an MR-compatible pedal. A 2nd MRI was performed for 11 CL and 6 PAD patients on a separate day. CE-MRI was performed on a 3T Siemens Trio scanner with infusion of 0.1mM/kg of gadolinium-DTPA followed by a 20 mL saline flush at 4 mL/s. A spoiled gradient echo dual contrast sequence with slices positioned 32 mm apart allowed for simultaneous acquisition of arterial input and muscle tissue function images. The slope of the time-intensity curves generated using ARGUS image analysis software (Siemens) for the arterial input and the muscle group with the highest signal intensity gave the arterial input function (AIF) and tissue function (TF). Perfusion Index (PI) is TF/AIF. PR is Ex TF/rest TF. AIF and TF measurements were normalized to proton density for 7 CL and 6 PAD.
Results: Mean age was similar for CL and PAD (59±9 vs 60±11). Ex time in PAD was lower than CL (311±372 vs 802±450 seconds, p<0.02). Rest TF (CL 0.25±0.18, PAD 0.11±0.09, p= 0.1) is quite low and neither it nor AIF (CL 14.2±10.2, PAD 7.3±5.4, p=0.1) are reproducible (Table 1). PR is paradoxically greater in PAD than CL due to low rest TF (56±40 vs. 27±18, p=0.02) with moderate reproducibility. Normalized Ex TF and PI are most reproducible (Table 1).
Conclusions: Overall, CE-MRI indices of calf perfusion, especially tissue function and perfusion index, are more reproducible with exercise than at rest, primarily due to low rest values in PAD patients. Thus, perfusion reserve is not a useful measure in PAD.
- © 2011 by American Heart Association, Inc.