Which imaging technique utilizes short-lived radioisotopes produced in accelerators?

Positron emission tomography (PET) is a medical imaging technique that indeed utilizes short-lived radioisotopes produced in particle accelerators or nuclear reactors. In PET scans, these radioisotopes are typically isotopes such as carbon-11 or fluorine-18, which are incorporated into forms of glucose or other biologically relevant molecules. When these compounds are injected into the body, they emit positrons as they decay. When a positron encounters an electron, they annihilate each other, resulting in the emission of gamma rays. PET scanners detect these gamma rays, allowing for the visualization of metabolic processes in the body, providing critical information regarding diseases such as cancer.

In contrast, techniques like X-ray computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound do not use radioisotopes for imaging. CT scans primarily rely on X-rays, MRI utilizes strong magnetic fields and radio waves, and ultrasound employs high-frequency sound waves to create images of the body's internal structures. Thus, PET is the only technique listed that matches the criteria for using short-lived radioisotopes produced in accelerators.