Coloured 2D (left) and 3D (right) diffusion tensor imaging (DTI) magnetic resonance imaging (MRI) scans of nerve pathways (red, blue and green) in the brain of a 55 year old female patient with a lesion (pink in 3D scan) in the right 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.