11C-Methionine

Methionine (MET) is an essential α-amino acid which plays a role in several biochemical processes, such as biosynthesis of proteins. L-Methionine labeled with 11C acts as a positron emission tomography tracer, as it is involved in synthesis of proteins in brain tumors. Normal brain tissue recognizes only glucose as a metabolic substrate (thus having a very low physiological 11C-methionine uptake), whereas tumoral brain tissues present an increased 11C-methionine uptake. This makes the signal-to-noise ratio quite high, thus helping in reading and interpreting PET scans. 11C-Methionine PET is easy and fast to perform. Usually 370–740 MBq of tracer is injected intravenously and, because of the short half-life of 11C-labeled molecules (20 min), the uptake time ranges from only 10 to 30 min. 11C-Methionine PET is a useful diagnostic and therapeutic tool in neuro-oncology. It has a high sensitivity in identifying primary brain tumors (histologic grading, define the extent of tumor, identify optimal biopsy sites), metastases, recurrence, in radiotherapy planning and in the assessment of response to therapy. Additionally, it allows the study of myocardial infarction, hyperparathyroidism, squamous cell head and neck cancer, multiple myeloma, and lymphoma.