Differentiation between high and low grade tumours in paediatric patients by using apparent diffusion coefficients

Objective: This study was performed to confirm the hypothesis that pre-operative apparent diffusion coefficient (ADC) can be used to distinguish between "low grade" and "high grade" tumours in paediatric patients.

Material and methods: ADC values were retrospectively evaluated in thirty-six paediatric brain tumours. Twenty-one children with low grade brain tumours (12 WHO I astrocytomas, 1 giant cell tumour, 1 pilomyxoid astrocytoma, 4 WHO II astrocytomas, 2 craniopharyngiomas and 1 ganglioglioma) and 15 children with high grade brain tumours (6 medulloblastomas, 3 WHO III ependymomas, 1 PNET, 1 malignant rhabdoid tumour, 1 malignant germ cell tumour, 1 WHO III astrocytoma, 1 WHO IV astrocytoma, 1 rhabdomyosarcoma metastasis) were included in this study. Minimum and mean ADC values were compared between low grade and high grade tumours and cut-off values were evaluated.

Results: The cut-off values to differentiate low and high grade paediatric brain tumours were 0.7 × 10(-3) mm(2)/s and 1.0 × 10(-3) mm(2)/s for minimum ADC and average ADC values respectively. All but one high grade infratentorial ependymoma showed significantly lower ADC values than low grade brain tumours in children.

Conclusion: Combining the information obtained from conventional MR imaging with the ADC values may increase the accuracy of pre-operative differentiation between low grade and high grade paediatric tumours. Cut-off values can help to discern low from high grade tumours. However, it has to be considered that there is a substantial overlap between tumour types previously described in the literature.