Perfusion Weighted MR Imaging may Differentiate Primary CNS Lymphoma from other Homogeneously Enhancing Brain Tumors

Primary central nervous system lymphoma (PCNSL), glioblastoma multiforme (GBM) and metastases may be difficult to differentiate based on conventional imaging alone. The aim of this study was to investigate the value of perfusion weighted imaging (PWI) in differentiating homogeneously enhancing PCNSL from homogeneously enhancing GBM and metastases. Seven consecutive patients presenting with homogeneously enhancing intraaxial tumors on MRI were retrospectively analyzed. All seven patients (three immunocompetent patients with PCNSL, three with GBM, and one with cerebral metastases) were examined with identical MR-sequences including PWI. The relative regional Cerebral Blood Volume (rrCBV) and the rrCBV ratio (rrCBVratio) were calculated. In lymphomas rrCBVratio was 0.93 ± 0.42 (mean ± SD) compared with 7.93 ± 1.44 in GBM and metastases. All lymphomas had rrCBVratio < 1.43 while all GBM and metastases had rrCBVratio > 1.43 (Fischer exact test; p < 0.001). PWI may be a valuable method in differentiating homogenously enhancing PCNSL from GBM and metastases.