Concomitant diminishing magnetization-transfer effect and increasing choline level in radiation-induced temporal-lobe changes

This article reports on the use of both magnetization-transfer (MT) imaging and 1H-MR spectroscopy in two cases of bilateral temporal-lobe changes after radiation therapy for nasopharyngeal carcinoma. In the first case, the following patterns were noted: although the temporal lobes appeared relatively normal on T2-weighted MR imaging, corresponding MT imaging clearly showed signal abnormalities (decreased MT effect) consistent with alterations in macromolecular structure; and concomitant strongly elevated choline on 1H-MR spectroscopy was observed, and this is associated with metabolic changes in cell membranes. The second case presented similar characteristics. In addition, there was an increased lactate signal and T2 signal changes in keeping with established oedema. Both MT and proton-spectroscopic findings were consistent with postulated pathophysiological features of radiation injury, but their specificity for this condition remains unclear. Magnetization-transfer imaging, and possibly 1H-MR spectroscopy, might be sensitive techniques for the early detection of late radiation injury. Copyright (2002) Blackwell Science Pty Ltd