Which imaging modality relies on the principles of nuclear medicine?

The choice of PET scan as the imaging modality that relies on the principles of nuclear medicine is accurate because PET, or Positron Emission Tomography, involves the use of radioactive substances that emit positrons. These radioactive tracers are administered to the patient, often through injection, and are typically labeled with a positron-emitting isotope like fluorine-18.

As the labeled glucose or other compounds decay, they emit positrons, which collide with electrons in the body, leading to the release of gamma rays. This emission is detected by the PET scanner, allowing for the visualization and measurement of metabolic processes in tissues and organs. This ability to provide insights into physiological functions, rather than just anatomical structures, is a hallmark of nuclear medicine.

In contrast, MRI relies on magnetic fields and radio waves to produce images of the body without the use of ionizing radiation; CT scans use X-rays to create cross-sectional images of the body; and ultrasound employs sound waves to visualize soft tissues and organs. None of these modalities utilize radioactive tracers or the principles inherent to nuclear medicine, making PET the correct answer in this context.