MODEL RELEASED. PET scan. Patient about to undergo a positron emission tomography (PET) brain scan. The patient is on a trolley that slides into the scanner's cavity. The head is restrained in order to prevent it from moving during the scan. The PET scanner analyses metabolic activity in the brain and other organs. It detects the presence of radioactive tracer molecules that have been injected into the patient's bloodstream and absorbed into the tissues. Abnormal metabolic activity may be diagnostic of tumour growth or internal injury. Photographed at the PET/ Biomedical Cyclotron Unit of Erasme Hospital, Brussels, Belgium.