Complex sentence: External beam radiotherapy otherwise known as teletherapy, is the most common form of radiotherapy where a patient lies on a couch and an external source of X-rays is pointed at a particular part of the body.
Split into simpler sentences: External beam radiotherapy otherwise known as teletherapy, is the mostfrequently used form of radiotherapy. The patient sits, or lies on a couch and an external source of X-rays is pointed at a particular part of the body.