Atypical imaging features of primary central nervous system lymphoma that mimics glioblastoma: utility of intravoxel incoherent motion MR imaging.

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. 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-one-out cross-validation and intraclass correlation coefficients were assessed to determine reliability and reproducibility of the parameters, respectively. Mean maximum f was significantly higher in the glioblastoma group than in the atypical PCNSL group (reader 1, 0.101 ± 0.016 [standard deviation] vs 0.021 ± 0.010; P < .001; reader 2: 0.107 ± 0.024 vs 0.027 ± 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). IVIM imaging can be used as a noninvasive imaging method to differentiate malignant brain tumors that show similar conventional MR imaging features.