Coloured diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) scan of nerve pathways (red, blue and green) in the brain of a 44 year old male patient with a large lesion in the left temporoparietal region. The lesion is probably a glioblastoma, a malignant (cancerous) tumour that arises from the supporting glial cells in the brain. Diffusion tensor imaging measures the direction of water diffusion, which in the brain reveals the orientation of nerve fibres. Red fibres have a left to right orientation, green a front to back orientation and blue an up and down orientation. The lesion is causing a lateral displacement of some nerve fibres in the right hemisphere and a more chaotic displacement of nerve fibres in the left hemisphere.