Which imaging modality utilizes electromagnetic waves in the radiofrequency spectrum?

Magnetic Resonance Imaging (MRI) is the modality that utilizes electromagnetic waves in the radiofrequency spectrum. MRI works by applying a strong magnetic field to the body, causing nuclei of specific atoms (primarily hydrogen, which is abundant in water and fat) to align with the field. When radiofrequency pulses are applied, these nuclei are momentarily disturbed from their alignment. Once the radiofrequency pulse is turned off, they return to their original state, emitting signals that are detected and processed to create detailed images of internal structures.

The unique ability of MRI to provide high-resolution images of soft tissues, such as muscles, brain, and connective tissues, is due to this interaction between the magnetic field and radiofrequency energy. This is in contrast to other modalities like X-ray and Computed Tomography, which use ionizing radiation, and Positron Emission Tomography, which involves radioactive tracers and their decay. Understanding this fundamental difference is crucial, as each imaging technique has its own applications based on the type of information needed and the safety considerations regarding radiation exposure.