Exercise-induced changes in magnetization transfer contrast of muscles.

Magnetization transfer contrast (MTC) technique provides a new type of contrast in MR imaging. The MTC method is based on the interaction between the spins of free protons and those with restricted motion. Exercise-induced changes in signal intensity and MTC were measured in the forearm muscles of 10 volunteers at 0.1 T. There was 26% increase in signal intensity of active flexor muscles after exercise when imaged with ordinary gradient echo sequence. Despite this marked intensity increase, the postexercise values of MTC did not differ from the preexercise ones.