Diffusion and perfusion MR patterns of central nervous system lymphomas

Central nervous system lymphomas (CNSLs) are rare tumors which may show variable appearance in standard magnetic resonance imaging (MRI) depending on their origin (primary or secondary) or patients' immunological status.

The aim of the study was to analyze imaging patterns of different CNSLs, using diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI).

Our material consisted of 16 CNSLs (14 primary, 2 secondary, 13 immunocompetent, 3 immunodeficient) which underwent magnetic resonance (MR) examinations including DWI and T2* dynamic susceptibility contrast (DSC) perfusion (without a preload in 13 cases, with a preload in 3 subjects). In DWI, apparent diffusion coefficient (ADC), and in PWI, parameters of relative cerebral blood volume (rCBV), relative peak height (rPH) and relative percentage of signal recovery (rPSR) were analyzed within the entire tumor (mean values) and in regions with minimal diffusion (ADCmin) and maximal perfusion values (rCBVmax, rPHmax, rPSRmax).

All CNSLs showed low values of ADCmean (0.70 × 10-3), ADCmin (0.54 × 10-3), rCBVmean (0.80), rCBVmax (1.27), rPHmean (1.05), rPHmax (1.59), as well as high values of rPSRmean (1.99) and rPSRmax (2.41). There were no significant differences in rCBVmax, as well as in all ADC, rPH and rPSR values between primary and secondary CNSLs or between tumors in immunocompetent and immunodeficient patients. Dynamic susceptibility contrast PWI with a preload resulted in significantly higher rCBV, rPH and lower rPSR values.

Despite various MR appearances, both primary and secondary CNSLs in immunocompetent and immunodeficient patients show very typical patterns of restricted diffusion and hypoperfusion with signal intensity curves returning above the baseline. Dynamic susceptibility contrast perfusion without a preload is recommended.