T2*-weighted and arterial spin labeling MRI of calf muscles in healthy volunteers and patients with chronic exertional compartment syndrome: preliminary experience.

OBJECTIVE. The purpose of our study was to assess temporal changes with exercise in T2* and arterial spin labeling signals in patients with chronic exertional compartment syndrome of the anterior compartment of the lower leg and in control subjects using T2* mapping and arterial spin labeling MRI. SUBJECTS AND METHODS. This prospective study was approved by the institutional research ethics board. Ten control subjects (five women and five men; mean age, 29.0 years) and nine patients with chronic exertional compartment syndrome (three women and six men; mean age, 33.7 years) gave informed written consent and underwent MRI of the calf muscles using an axial T2*-weighted multiecho gradient-recalled echo and a flow-sensitive alternating inversion recovery sequence with echo-planar imaging readouts before (baseline) and 3, 6, 9, 12, and 15 minutes after exercise. T2* and arterial spin labeling signal changes (Delta T2* and Delta ASL, respectively) over time were calculated relative to the baseline examination. Delta T2* and Delta ASL between patients and control subjects were compared using the Student's t test. RESULTS. In both patients and control subjects, Delta T2* and Delta ASL showed a peak at 3 minutes after exercise, followed by a decrease over time. The maximum Delta T2* was 26% and 29% for patients and control subjects, respectively. The maximum Delta ASL was 183% and 224% for patients and control subjects, respectively. After 15 minutes, arterial spin labeling signal returned to baseline; however, T2* remained elevated (8% in patients; 10% in control subjects). No statistically significant differences between patients and control subjects in postexercise Delta T2* and Delta ASL were found (p = 0.21-0.98). CONCLUSION. After calf muscle exercise, no statistically significant differences in T2* relaxation times or arterial spin labeling signal, indicative of differences in muscle oxygenation and perfusion status, were found between patients with chronic exertional compartment syndrome and control subjects.