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

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 4000s/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 (3T) magnetic resonance (MR) instrument.

Materials and methods

This study was approved by our Institutional Review Board. We acquired DWI at 3T with b=1000 and b=4000s/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 (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=1000s/mm². 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=0.500×10⁻³mm²/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-4000s/mm² at 3T MRI.

Abbreviations: MR, magnetic resonance, ADC, apparent diffusion coefficient, ADC_MIN, minimum absolute values of apparent diffusion coefficient, ADC_MEAN, mean absolute values of apparent diffusion coefficient, ADC_MAX, maximum absolute values of apparent diffusion coefficient, DWI, diffusion-weighted images, CNS, central nervous system, b-1000, b 1000s/mm², standard b value, b-4000, b 4000s/mm², high b value, 3T, 3-Tesla, FLAIR, fluid-attenuated inversion recovery, ROI, region of interest, TR, repetition time, TE, echo time, FOV, field of view

Keywords: Lymphoma, Glioblastoma, ADC, High b value, Cellularity