Atypical Imaging Features of Primary Central Nervous System Lymphoma That Mimics Glioblastoma: Utility of Intravoxel Incoherent Motion MR Imaging

Purpose: To determine the utility of intravoxel incoherent motion (IVIM)-derived perfusion and diffusion parameters for differentiation of atypical primary central nervous system lymphoma (PCNSL) from glioblastoma in patients who do not have acquired immunodeficiency syndrome. Materials and Methods: The institutional review board approved this retrospective study and waived the informed consent requirement. Sixty patients with either pathologic analysis-confirmed atypical PCNSLs (n = 19) or glioblastomas (n = 41) were assessed by using maximum IVIM-derived perfusion fraction (f) and minimum true IVIM diffusion parameter (D). Two readers independently calculated IVIM parameters and maximum normalized cerebral blood volume (nCBV) and minimum apparent diffusion coefficient. Leave-oneout cross-validation and intraclass correlation coefficients were assessed to determine reliability and reproducibility of the parameters, respectively. Results: Mean maximum f was significantly higher in the glioblastoma group than in the atypical PCNSL group (reader 1, 0.101 6 0.016 [standard deviation] vs 0.021 6 0.010; P,.001; reader 2: 0.107 6 0.024 vs 0.027 6 0.015; P,.001). Mean minimum D did not significantly differ between the two groups (reader 1, P =.202; reader 2, P =.091). By using maximum f as a discriminative index, respective sensitivity and specificity were 89.5% and 95.1% for reader 1 and 84.2% and 95.1% for reader 2. There was a significant positive correlation between maximum f and the corresponding nCBV (r = 0.68; P,.001). The intraclass correlation coefficient between readers was highest for measurement of maximum f (intraclass correlation coefficient, 0.92). Conclusion: IVIM imaging can be used as a noninvasive imaging method to differentiate malignant brain tumors that show similar conventional MR imaging features. q RSNA, 2014