Abstract
Purpose
To detect skeletal muscle ischemia with first‐pass gadolinium (Gd) kinetics after exercise.
Materials and Methods
Eleven subjects with intermittent claudication performed a symptom‐limited bilateral plantar flexion exercise in the magnet. Regional ROIs were placed bilaterally in the gastrocnemius and soleus muscles, and a signal intensity (SI) time‐curve analysis was performed. Induced ischemia was validated prior to the MRI with the systolic ankle‐arm blood pressure index (AAI) measured after a symptom‐limited treadmill exercise.
Results
Exercise induced ischemic pain in 16 of 22 legs with a significantly reduced AAI (0.31 ± 0.15). The time to contrast arrival (TCA) was delayed in symptomatic ischemic legs vs. asymptomatic legs (16.3 ± 6.9 seconds vs. 11.1 ± 2.7 seconds, P < 0.05). The maximum SI during recovery was higher in the soleus muscle than in the gastrocnemius muscle in ischemic legs (1.55 ± 0.1 vs. 1.44 ± 0.1, P < 0.05). Symptomatic regions had a less steep upslope than asymptomatic regions (43 ± 15 vs. 63 ± 14, P < 0.001), with a graded upslope response to ischemia. However, a normal upslope was found in 10 of 29 ischemic regions, and some of the regions showed delayed contrast arrival, suggesting a pseudonormal upslope in ischemic regions.
Conclusion
Exercise‐induced ischemia was detected with the use of an SI time‐curve analysis. However, disregarding the arterial input function and distribution volume of the tracer may lead to misinterpretation of some ischemic regions. J. Magn. Reson. Imaging 2006. © 2005 Wiley‐Liss, Inc.