Feasibility study of computed high b-value diffusion-weighted magnetic resonance imaging for pediatric posterior fossa tumors.

Purpose: To evaluate the diagnostic efficacy of computed diffusion-weighted imaging (DWI) in pediatric posterior fossa tumors generated using high b-values.

Methods: We retrospectively performed our study on 32 pediatric patients who had undergone brain magnetic resonance imaging for a posterior fossa tumor between January 2016 and January 2022. The DWIs were evaluated for each patient by two blinded radiologists. The computed DWI (cDWI) was mathematically derived using a mono-exponential model from images with b = 0 and 1,000 s/mm² and high b-values of 1,500, 2,000, 3,000, and 5,000 s/mm². The posterior fossa tumors were divided into two groups, low grade and high grade, and the tumor/thalamus signal intensity (SI) ratios were compared. The Mann-Whitney U test and receiver operating characteristic (ROC) curves were used to compare the diagnostic performance of the acquired DWI (DWI₁₀₀₀), apparent diffusion coefficient (ADC)₁₀₀₀ maps, and cDWI (cDWI1500, cDWI₂₀₀₀, cDWI₃₀₀₀, and cDWI₅₀₀₀).

Results: The comparison of the two tumor groups revealed that the tumor/thalamus SI ratio on the DWI₁₀₀₀ and cDWI (cDWI1500, cDWI₂₀₀₀, cDWI₃₀₀₀, and cDWI₅₀₀₀) was statistically significantly higher in high-grade tumors (P < 0.001). In the ROC curve analysis, higher sensitivity and specificity were detected in the cDWI1500, cDWI₂₀₀₀, cDWI₃₀₀₀, and ADC₁₀₀₀ maps (100%, 90.90%) compared with the DWI₁₀₀₀ (80%, 81.80%). cDWI₃₀₀₀ had the highest area under the curve (AUC) value compared with other parameters (AUC: 0.976).

Conclusion: cDWI generated using high b-values was successful in differentiating between low-grade and high-grade posterior fossa tumors without increasing imaging time.

Clinical significance: cDWI created using high b-values can provide additional information about tumor grade in pediatric posterior fossa tumors without requiring additional imaging time.