Diffusion-weighted imaging and susceptibility-weighted imaging in differentiating ring-enhancing primary central nervous system lymphoma from infections

IntroductionDifferentiating ring-enhancing primary central nervous system lymphoma (PCNSL) from infections is critical yet challenging in clinical practice. This study aimed to evaluate the effectiveness of diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI) in differentiating ring-enhancing PCNSL from infections.Material and MethodsWe retrospectively reviewed 78 ring-enhancing lesions in 32 patients who underwent brain magnetic resonance imaging (MRI). Qualitative and quantitative assessments of the peripheral and central regions of ring-enhancing lesions were independently performed. The qualitative assessment involved evaluating restricted diffusion on DWI and intralesional susceptibility signal (ISS) on SWI. The quantitative assessment involved comparing the apparent diffusion coefficient average (ADC avg ) ratio and apparent diffusion coefficient minimum (ADC min ) ratio of the peripheral and central regions with the final diagnosis.ResultsThe lesions consisted of PCNSL ( n = 21), tuberculosis ( n = 17), and toxoplasmosis ( n = 40). The qualitative assessment showed that diffusion was significantly more restricted at the periphery in PCNSL ( p p p = .001) in PCNSL than in infections. The quantitative assessment revealed that PCNSL had significantly lower ADC avg (peripheral, p p = .01) and ADC min ratios (peripheral, p p = .025) compared to infections. A peripheral ADC avg ratio of <1.25 demonstrated the best diagnostic accuracy (area under the curve: 0.966, 95% confidence interval [CI]: 0.93-1.00, sensitivity: 85.7%, specificity: 89.5%, and accuracy: 88.5%) for differentiating PCNSL from infections.ConclusionRestricted diffusion on DWI, positive ISS on SWI, and ADC ratio measurements of ring-enhancing lesions demonstrate significant potential as adjunctive imaging features for distinguishing PCNSL from CNS infections.