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

Background and purposeAs 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/mm2 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 methodsThis study was approved by our Institutional Review Board. We acquired DWI at 3 T with b = 1000 and b = 4000 s/mm2 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 (ADCMIN, ADCMEAN, ADCMAX). We evaluated the relationship between ADCs and histological information including tumor cellularity.ResultsAll ADC values were statistically associated with tumor cellularity. ADCMIN at b-4000 was associated with tumor cellularity more significantly than ADCMIN 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/mm2. According to the results of discriminant analysis, the log likelihood was greatest for ADCMIN at b = 4000. At a cut-off value of ADCMIN = 0.500 × 10−3 mm2/s at b-4000 it was possible to differentiate between lymphoma and glioblastoma (sensitivity 90.9%, specificity 91.7%).ConclusionsCalculating 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 ADCMIN at b-4000 s/mm2 at 3 T MRI.