Using light rays during extracorporeal therapy is known as what?

Phototherapy is the correct term used to describe the application of light rays in a therapeutic context, particularly during extracorporeal treatments. This method involves using specific wavelengths of light to treat various medical conditions, which may include skin disorders, neonatal jaundice, and certain types of cancer. Phototherapy works by utilizing the effects of light to promote healing, reduce inflammation, or alleviate pain.

The other options refer to different modalities or techniques. Radiotherapy involves the use of high-energy radiation to target and kill cancer cells, often using X-rays or gamma rays, which is distinct from the light-based treatment in phototherapy. Ultrasonography utilizes high-frequency sound waves to create images of organs and structures within the body; it does not involve light rays. Optotherapy, though it may seem related to phototherapy, is not a standard term used in medical practice and does not hold the same recognition as phototherapy in clinical settings. Thus, phototherapy is the most accurate term for using light rays in extracorporeal therapy.