Lymphomas and glioblastomas: Differences in the apparent diffusion coefficient evaluated with high b-value diffusion-weighted magnetic resonance imaging at 3 T

Abstract Background and purpose As the usefulness of the apparent diffusion coefficient (ADC) obtained from diffusion-weighted images (DWI) for the differential diagnosis between glioblastoma and primary central nervous system lymphoma is controversial, we assessed whether high b -value DWI at b 4000 s/mm 2 could discriminate between glioblastoma and lymphoma. We also compared the power of high- and standard b -value ( b -4000, b -1000) imaging on a 3-Tesla (3 T) magnetic resonance (MR) instrument. Materials and methods This study was approved by our Institutional Review Board. We acquired DWI at 3 T with b  = 1000 and b  = 4000 s/mm 2 in 10 patients with lymphoma and 14 patients with glioblastoma. The ADC was measured by placing multiple regions of interest (ROI) on ADC maps of the site of enhanced lesions on contrast-enhanced T1-weighted MR images. We avoided hemorrhagic and cystic lesions by using T1-, T2-, FLAIR-, and T2* MR images. The ADC values of each tumor were determined preoperatively from several ROI and expressed as the minimum-, mean-, and maximum ADC value (ADC MIN , ADC MEAN , ADC MAX ). We evaluated the relationship between ADCs and histological information including tumor cellularity. Results All ADC values were statistically associated with tumor cellularity. ADC MIN at b -4000 was associated with tumor cellularity more significantly than ADC MIN at b -1000. All ADC values were lower for lymphoma than glioblastoma and the statistical difference was larger at b  = 4000- than b  = 1000 s/mm 2 . According to the results of discriminant analysis, the log likelihood was greatest for ADC MIN at b  = 4000. At a cut-off value of ADC MIN  = 0.500 × 10 −3  mm 2 /s at b -4000 it was possible to differentiate between lymphoma and glioblastoma (sensitivity 90.9%, specificity 91.7%). Conclusions Calculating the ADC value is useful for distinguishing lymphoma from glioblastoma. The lowest degree of overlapping and a better inverse correspondence with tumor cellularity were obtained with ADC MIN at b -4000 s/mm 2 at 3 T MRI.