Which of the following modalities uses ionizing radiation?

The use of ionizing radiation is a defining characteristic of certain imaging modalities, primarily those that rely on the interaction of radiation with matter to produce images. X-ray imaging is a classic example of this, as it utilizes ionizing radiation to penetrate body tissues and create images based on the differing densities of those tissues.

Computed Tomography (CT) also employs ionizing radiation as it combines multiple X-ray images to create cross-sectional views of the body, providing more detailed information than standard X-ray methods. Therefore, both X-ray and CT involve ionizing radiation.

In contrast, ultrasound and magnetic resonance imaging (MRI) do not use ionizing radiation. Ultrasound relies on high-frequency sound waves to generate images, while MRI uses powerful magnetic fields and radio waves to produce detailed images of organs and soft tissues.

Understanding the distinction between modalities that use ionizing radiation and those that do not is crucial in both patient safety and in the appropriate selection of imaging techniques based on the clinical scenario.