Indications for differential diagnosis of nontumor central nervous system diseases from tumors. A positron emission tomography study.

To accurately differentiate nontumor central nervous system (CNS) diseases from brain tumors, we retrospectively evaluated the cerebral circulation and metabolism in patients with nontumor CNS diseases using positron emission tomography (PET). Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), the metabolic rates of oxygen (rCMRO2), and of glucose (rCMRGI), and the uptake of 11C-methyl-L-methionine (11C-Met) were visually evaluated in lesions and compared with values for the contralateral white matter regions. PET findings were correlated with those of x-ray computed tomography (CT) and magnetic resonance imaging (MRI), and were analyzed for nontumor CNS diseases and cerebral gliomas. rCBF and rCBV were changeable from disease to disease or from stage to stage of disease progression. rOEF and rCMRO2 remained low in 5 and 6, respectively, of 9 nontumor CNS diseases examined, whereas these parameters were increased in CNS infections such as brain abscess. Overall, noteworthy was the locally increased rOEF and rCMRO2 in the patients with a brain abscess in contrast to the values for patients with gliomas. rCMRGI reflected biological characteristics of each disease, and correlated with cell density, whether reactive glial cells or inflammatory cells. 11C-Met was accumulated at a certain stage of nontumor CNS diseases, which implied uptake of the tracer as a result of disruption of the blood-brain barrier as well as metabolic incorporation.