Brain scan. Falsecolour magnetic resonance imaging (MRI) scan of a human head containing a healthy brain, seen in horizontal view. At lower frame is the cerebrum (yellow), the largest region of the brain, highly convoluted and divided into two hemispheres. Between these cerebra is the mid brain (at centre) and beneath it a small region of the cerebellum. At upper frame, the two eyeballs can be seen (black) with an optic nerve leading from each to the brain. Between the eyes is the nasal cavity containing the concha, thin scroll like bones. MRI scanning is a diagnostic technique in which a powerful electromagnet and radio waves create crosssection images of body regions.