Diagnostic value of kinetic analysis using dynamic FDG PET in immunocompetent patients with primary CNS lymphoma

The purpose of this study was to investigate the accumulation of FDG in immunocompetent patients with primary central nervous system (CNS) lymphoma using qualitative and quantitative PET images and to compare baseline with follow-up PET after therapy. Twelve immunocompetent patients with CNS lymphoma were examined. Dynamic emission data were acquired for 60 min immediately following injection of FDG. In seven patients, repeated PET studies were performed after treatment. Applying a three-compartment five-parameter model, K1, k2, k3, k4, vascular fraction (VB) and cerebral metabolic rate of glucose (CMRGlc) were obtained. We evaluated the FDG uptake visually using qualitative and parametric images and quantitatively using parametric images. A total of 12 lesions were identified in ten patients with newly diagnosed CNS lymphoma. On visual analysis, ten lesions showed an increase on qualitative images, eight showed an increase on K1 images, 12 showed an increase on k3 images and ten showed an increase on CMRGlc images. On quantitative analysis, k2, k3 and CMRGlc values of the lesion were significantly different from those of the normal grey matter (p <0.02-0.0005). A total of three lesions were identified in two patients with recurrent tumour. All three lesions showed an increase on qualitative, k3 and CMRGlc images. The K1, k2, k3 and CMRGlc values after treatment were significantly different from those obtained before treatment (p <0.04-0.008). Kinetic analysis, especially with respect to k3, using dynamic FDG PET might be helpful for diagnosis of CNS lymphoma and for monitoring therapeutic assessment. (orig.)