Utility of Apparent Diffusion Coefficient Ratios in Distinguishing Common Pediatric Cerebellar Tumors

Rationale and Objectives: The aim of this study was to identify clinically useful tumor/normal brain apparent diffusion coefficient (ADC) ratios for distinguishing common pediatric cerebellar tumors. Materials and Methods: Review of medical records revealed 79 patients with cerebellar tumors who underwent preoperative magnetic resonance imaging, including diffusion-weighted imaging sequences, and surgery. There were 31 pilocytic astrocytomas, 27 medulloblastomas, 14 ependymomas, and seven atypical teratoid/rhabdoid tumors. ADC values were measured by placing regions of interest on the solid tumor and normal brain parenchyma by two reviewers. Tumor/normal brain ADC ratios were calculated. Results: Mean ADC values of the pilocytic astrocytomas were greater than those of ependymomas, whose mean ADC values were greater than those of medulloblastomas and atypical teratoid/rhabdoid tumors. Using a tumor/normal brain ADC ratio threshold of 1.70 to distinguish pilocytic astrocytomas from ependymomas, sensitivity of 92% and specificity of 79% were achieved. A tumor/normal brain ADC ratio threshold of 1.20 enabled the sorting of ependymomas from medulloblastomas with sensitivity of 93% and specificity of 88%. Conclusions: Tumor/normal brain ADC ratios allow the distinguishing of common pediatric cerebellar tumors.