Treadmill exercise does not affect image quality on subsequent whole body FDG PET scan

Objectives It is widely believed that physical exercise prior to whole body FDG PET increases muscle FDG uptake and deteriorates PET image quality, but this has not been studied systematically. We determined the effects of low to moderate level treadmill exercise on FDG uptake in skeletal muscles and on image quality of subsequent whole body PET scans. We also compared patterns of myocardial FDG uptake with stress myocardial perfusion imaging (MPI) findings.

Methods 48 pts. underwent FDG PET within 8 hrs after treadmill exercise (Group A); 45 pts within 48 hrs after treadmill test (group B), and 34 pts without prior exercise (group C). Patient distribution: 69 M/58F; mean age:62 yrs, range: 30-80 yrs. Mean workload (8.4+/-2.3 versus 8.9+/-2.6 METS) was similar in groups A and B. FDG uptake time and blood glucose were similar in all 3 groups. SUVs were computed for quadriceps and gluteal muscles in all 3 pt groups, as well as for liver and spine (for background activity). Upper extremity and chest wall muscle uptake was compared visually. Myocardial FDG distribution was compared to the SPECT Tl-201/Tc-99m tetrofosmin MPI findings.

Results Minor differences between groups A, B, and C were only noted for SUV max in the quadriceps muscle(SUVmax 1.41+/-0.41 vs 1.21+/-0.48 vs 1.36+/-0.22; p=0.035), but not for any other parameter. Image quality and visual assessment of other muscles were also similar. Only 4 pts in group A had at least moderate ischemia and 2 had infarcts on MPI. There was no correlation between MPI and myocardial FDG patterns.

Conclusions Treadmill exercise test preceding FDG PET does not affect physiologic skeletal muscle FDG uptake and PET image quality in a clinically significant manner. It appears acceptable to schedule treadmill stress test on the same day prior to FDG PET. Myocardial FDG uptake is largely unrelated to MPI findings