Correlative studies of the brain with positron emission tomography (PET), nuclear magnetic resonance (NMR) and x-ray computed tomography (XCT)

Twenty-four patients with a variety of CNS disorders were examined with NMR, PET and XCT within a short period of time. NMR images were obtained using an experimental 0.12 Tesla resistive magnet. Partial saturation technique was used to acquire NMR images either as two-dimensional single axial plane or as three-dimensional volume images. PET imaging was performed following the administration of 18F-fluorodeoxyglucose. In nine patients with brain tumor all three modalities identified the neoplastic lesion. XCT provided a better differentiation of tumor from surrounding edema than NMR. PET was most accurate in determining the histologic grade of the tumor. In one patient with acute stroke NMR failed to identify the CNS abnormality. In the remaining three patients the findings on the NMR images correspond well to those seen on the XCT. PET images demonstrated metabolic abnormalities which usually appeared more extensive. The presence of ventricular dilation and cortical atrophy was demonstrated by both NMR and XCT, although the latter appeared more pronounced with NMR. PET studies showed pronounced reduction in posterior temporoparietal region metabolism in patient with dementia. In patients with seizure and psychotic disorders, while PET showed certain abnormal patterns, both XCT and NMR appeared normal. These data indicate that NMR provides excellent delineation of structural changes compared to those seen by XCT. PET imaging on the other hand demonstrates regional metabolic activity which compliments anatomic findings on XCT and NMR