Value of diffusion-weighted imaging in grading tumours localized in the fourth ventricle region by visual and quantitative assessments.

This study investigated visual and quantitative assessment of diffusion-weighted imaging (DWI) for grading tumours localized in the fourth ventricle region. Patients were diagnosed histopathologically and classified into two groups: those with high-grade (World Health Organization [WHO] grades III and IV) and those with low-grade tumours (benign, WHO grades I and II). DWI signal intensity was described using a five-point scale. Minimum apparent diffusion coefficient (ADC) values were obtained from areas with the lowest signal. The mean signal intensity was significantly higher in high-grade than in low-grade tumours. The mean minimum ADC value was significantly lower in high-grade than low-grade tumours. Marked hyperintensity had sensitivity, specificity, positive predictive value and negative predictive value of 89.7%, 100%, 100% and 94.2%, respectively, when used as a diagnostic tool for high-grade tumours compared with 96.6%, 97.9%, 96.6% and 97.9%, respectively, when using a minimum ADC of 0.9 × 10(-3) mm(2)/s as a diagnostic marker. It was concluded that DWI is helpful in predicting the grades of tumours in the fourth ventricle region.