MODEL RELEASED. Brain biopsy. Neurosurgeon performing a brain tissue biopsy. He is guiding a needle into an incision in the skull using a frame. The skull is held open using retractor forceps. The frame gives a very high degree of accuracy in finding positions, and also stabilises the needle. This is a stereotaxic operation: the head of the patient has been scanned (by MRI, CT or PET scanning) to determine the ideal area to take the biopsy from. This reduces the chance of damaging healthy brain tissue. Tissue is removed and then analysed to establish a diagnosis. Brain biopsies are most frequently performed in cases of suspected brain tumour.