Comparison of 18F-FDG PET imaging and MRI of intracranial primary malignant lymphoma

Objective: The most common encountered intracranial malignant tumors included glioblastomas, metastatic tumors and intracranial primary malignant lymphomas (IPML). The aim of the study was to comparatively analyze the 18F-FDG PET manifestations of the three tumors, in particular the image features of IPML. Methods: Ten IPML, 20 glioblastomas and 15 cerebral metastases underwent 18F-FDG PET. The images were analyzed on the basis of lesion location, uptake value and distribution pattern of FDG. Ratios of tumor to contralateral corresponding region (T/CCR) and of cortex surrounding tumor to the contralateral cortex (TSC/CCRC) were measured using ROI method. Results: In 10 IPML, there were 6 cases with solitary focus located on the cerebra surface and 4 multiple lesions neighboring to the midline of brain, basal ganglia and thalamus. All lesions presented as intensely hypermetabolic. There was also mild to moderate hypometabolism in the cortex around the lesions, 18F-FDG uptake in IPML was higher than glioblastomas and cerebral metastases, but the decrease accumulation of 18F-FDG in the cortex around IPML was less than that of the other two kinds of tumors. Conclusion: IPML presented on PET images as solitary or multiple foci with higher hypermetabolic change and less disturbance on 18F-FDG uptake in nearby cortex than those of glioblastoma and cerebral metastases, which might serve the purpose of differential diagnosis for intracranial tumors. (authors)