METHIONINE PET FOR FOLLOW-UP OF RADIATION-THERAPY OF PRIMARY LYMPHOMAOF THE BRAIN

Positron emission tomography (PET) with carbon-11 methionine, computed tomography (CT), and magnetic resonance (MR) imaging were performed i n 10 patients with histologically verified central nervous system (CNS ) lymphoma before and after radiation therapy to compare the radiologi c findings and to evaluate the usefulness of PET in monitoring tumor r esponse to radiation therapy. Methionine PET clearly depicted CNS lymp homa before radiation therapy as an increased accumulation of C-11 met hionine. The extent of increased accumulation of the radiotracer in tu mor tissue markedly decreased after radiation therapy. The area of inc reased uptake was larger than the enhancing lesions on CT or MR images in most cases. One patient was confirmed to have tumor recurrence at the region of residual increased accumulation on methionine PET images . Methionine PET is useful for the delineation of CNS lymphoma and for monitoring the therapeutic effect of irradiation.