Diagnostic Performance of DWI and ADC Parameter in Differentiating Brain Abscess from Malignant Ring-Enhancing Brain Lesions: A Systematic Review and Meta-analysis.

[PURPOSE] To assess the performance of diffusion-weighted imaging (DWI) and apparent diffusion coefficients (ADC) in the differentiation of brain abscesses (BA) from malignant ring-enhancing brain lesions (REBL).

[METHODS] The protocol was pre-registered at (https://osf.io/mjwek). We conducted a comprehensive search in PubMed, Embase, and Web of Science until April 5, 2025, for studies that used DWI for differentiation of malignant REBLs from BAs. The risk of bias in the included studies was evaluated using QUADAS-2. ADC were compared between malignant REBLs and BAs using a random-effects model. Diagnostic values of area under the curve (AUC), sensitivity, and specificity were calculated. Sensitivity analysis, publication bias tests, and subgroup analysis were performed.

[RESULTS] Thirty-four studies were included with 1382 malignant REBL and 1061 abscesses. The pooled ADC values of malignant REBL and BA were 1797.17 × 10 mm/s (95 % CI: 1446.55-2147.80) and 852.07 × 10 mm/s (95 % CI: 786.52-917.61). Malignant REBLs had 116 % higher ADCs than BAs with a significant pooled standardized mean difference of 3.12 (95 % CI: 2.32-3.91, I2 = 96.8 %, p < 0.001). Qualitative assessment of DWI and ADC parameter demonstrated a pooled sensitivity of 92 % (95 % CI: 89 %-95 %), specificity of 92 % (95 % CI: 89 %-94 %), and AUC of 0.97 (95 % CI: 0.95-0.98) for differentiating BAs from malignant REBLs.

[CONCLUSION] DWI provides a valuable diagnostic tool for differentiating BAs from malignant REBLs, demonstrating high sensitivity, specificity, and significant ADC difference between the two groups.