[11C-methionine PET, IMP-SPECT, CT and MRI in brain tumors]

11C-labelled L-methionine uptake was measured in 7 patients with brain tumours prior to surgery, and in 2 patients with infarction, using PET. The strongest uptake occurred in tumours with a high grade of malignancy (astrocytoma IV: Tumour/Non-Tumour T/NT = 2.6) while low-grade tumours accumulated less activity (astrocytoma II: T/NT = 1.4). Conventional 99mTc DTPA scans revealed a damage of blood brain barrier (BBB) in 4 patients (2 infarctions) with no or only slight 11C-methionine accumulation, while one patient with negative 99mTc-scan and negative CT accumulated methionine in the tumour region (astrocytoma II). PET, MRI, and CT are complementary with regard to extent of tumour tissue, necrotic areas and oedema. None of the brain tumours or infarcted regions took up IMP (123I amphetamine). The investigated regions showed definite uptake defects ranging from 10-50% if compared with the contralateral side. In view of the chemical pathway of methionine it is concluded that the uptake reflects metabolic activity in brain tumour tissue rather than a diffuse uptake due to BBB damage.