OP21
CHARACTERISING THE TRANSITION ZONE FROM TUMOUR TO NORMAL BRAIN IN GLIOBLASTOMAS USING MULTIMODAL MRI Free

INTRODUCTION: Identification of the invasive margin is a key limitation to treating Glioblastomas. Conventional T1-weighted and T2-weighted imaging methods are still used to assess the extent of tumour for resection. However, it is shown in histological specimens that malignant cells extend for several centimetres beyond the contrast enhancing regions. The transition between tumour edge, peritumoural oedema and normal brain remains ambiguous. Multi-modal MR (diffusion tensor, spectroscopy and perfusion) is a promising new imaging technique to study tumour invasion. An improvement in the understanding of the tumour margin would allow individualized tailoring of treatment. METHOD: 80 patients with glioblastomas were imaged pre-operatively at 3T with anatomical sequences, diffusion-tensor, dynamic susceptibility contrast and spectroscopy. Data was co-registered to the same imaging space. Regions of interest (ROIs) were selected in a circumferential consecutive pattern from the edge of the T1-weighted enhancing region to normal appearing brain. The parameters were calculated per voxel and expressed as a ratio to normal brain. RESULTS: The isotropic component of diffusion-tensor remained raised at a 30mm distance beyond the edge of the enhancing region (1.18 ± 0.02, p < 0.000 at 30mm). Perfusion was persistently elevated within each consecutive expanding circumference (1.56 ± 0.06 at 30mm). Choline remained raised in comparison to the contralateral hemisphere at 20mm (1.14 ± 0.04) beyond the edge of the T1-enhancing region. CONCLUSION: MRI biomarkers of tumour cell presence extend up to 3 cm beyond the conventionally determined tumour margin. Incorporating multimodal MRI data into treatment planning will allow more precise surgical resection and planning of radiotherapy.