Utility of apparent diffusion coefficients in the evaluation of primary central nervous system lymphoma.

摘要

The characterization of primary central nervous system lymphoma (PCNSL) via noninvasive imaging modalities is essential for early diagnosis and differentiation from other brain lesions. Diffusion-weighted magnetic resonance imaging (DW-MRI), in which intensity of image contrast reflects diffusion of water molecules by Brownian motion, offers additional information beyond that obtained from conventional MRI. In this retrospective study from two institutions, quantitative region of interest (ROI) analysis was performed using parametric apparent diffusion coefficient (ADC) maps in immunocompetent patients with newly diagnosed PCNSL prior to corticosteroid use or other therapy. Mean ADC values and ratios were calculated for PCNSL lesions, peritumoral edema, and contralateral normal white matter. Quantitative DW-MRI analysis (n=12) revealed significant inter- group variance between the mean ADC of lesion, peritumoral region, and normal white matter. Tukey post-hoc comparison of the three groups indicate that the mean ADC of the peritumoral region is significantly different (p0.05) from mean ADC of the lesion and normal white matter, while differences between mean ADC of the lesion and normal white matter were not statistically significant. A comprehensive review of prior investigations reporting ADC values in evaluation of PCNSL was also conducted. We found that restricted diffusion is a consistent imaging finding in immunocompetent PCNSL patients and a reliable surrogate marker of tumor cellularity; however, the ranges of ADC values reported for PCNSL varied between studies and also overlapped with ADC ranges reported for other brain tumors. Given the observed variability in ADC values, it is essential to consider DW-MRI data as an adjunct diagnostic tool interpretable only in the context of clinical presentation and conventional MRI data. Further prospective investigation enrolling patients prior to corticosteroid therapy will be necessary to obtain standardized pre-treatment ADC values.