Functional MRI of the Lower Extremities

In this project, the investigators propose to use high-resolution magnetic resonance imaging
(MRI) to measure blood perfusion in different groups of calf muscle. This imaging approach is
standard of care for evaluation of coronary artery disease (CAD), and has never been
successfully applied to PAD. Preliminary results show distinct patterns of muscle perfusion
between healthy and PAD patients, and thus great promise of the technique. The investigators
will first verify the reproducibility of the technique, and then compare the calf muscle
perfusion measures in PAD patients against healthy age-matched controls. This comparison will
test the feasibility of detecting functional abnormality in PAD patients. After the baseline
scans, the PAD patients will opt to undergo a 12-week supervised exercise therapy, and then a
post-therapy MRI scan. Comparison of the pre- and post-therapy measurements will indicate how
the therapy improves the calf-muscle perfusion, and how this perfusion change correlates with
increases in patient's walking ability.

The long term goals of this project are to develop an improved diagnostic test for patients
with PAD to predict who will benefit from therapeutic intervention. The MRI perfusion studies
of calf muscle can be performed in conjunction with routine peripheral MR angiography to
assess the functional significance of vascular stenosis.