MIPPA defines ADI services to include diagnostic CT, MRI, and NM, including positron emission tomography (PET).CT is an imaging modality that uses ionizing radiation and computers to produce crosssectional images of internal organs and body structures. MRI is an imaging modality that uses powerful magnets, radio waves, and computers to create cross-sectional images of internal body tissues. NM is the use of radioactive materials in conjunction with an imaging modality to produce images that show both structure and function within the body. During an NM service, such as a PET scan, a patient is administered a small amount of radioactive substance, called a radiopharmaceutical or radiotracer, which is subsequently tracked by a radiation detector outside the body to render time-lapse images of the radioactive material as it moves through the body.