Positron emission tomography (PET) scans are used to produce detailed three-dimensional images of the inside of the body. The images can clearly show the part of the body being investigated, including any abnormal areas, and can highlight how well certain functions of the body are working. PET scans are often combined with computerised tomography (CT) scans to produce even more detailed images. This is known as a PET-CT scan. They may also occasionally be combined with a magnetic resonance imaging (MRI) scan. This is known as a PET-MRI scan.