= radiotherapy, n.

Exposure to the action of some kind of radiation (other than visible light, as X-rays, ultra-violet radiation, or neutrons); the (or an) action or…

The treatment of disease, esp. cancer, by means of X-rays and other forms of ionizing radiation.

= ray treatment n.

medical treatment using radiation, esp. radiotherapy; an instance or session of this; (also) treatment of food or other material with radiation.

= radiotherapy, n.

Highly focused radiotherapy, esp. for the ablation of lesions of the brain. Esp. in stereotaxicor stereotactic radiosurgery.