Conventional radiation therapy

Conventional (2D) radiation therapy refers to the old techniques of radiation therapy where treatments would be planned by defining a limited number of beams with the boundaries delineated on orthogonal x-rays of the patient. It has been largely replaced by other highly conformal external beam radiation therapies, which use CT images to plan the treatment.

Beam shaping was limited and typically simple square or rectangular beams were used. A typical beam arrangement is the four field box. Due to the low conformity of these treatments, adjacent tissues/organs often fall into the high dose region resulting in treatment side effects. Also, the amount of radiation delivered to the targeted tumor is usually not adequate resulting in less effective treatment .

Although 2D radiotherapy is now rarely used, it still has a role in palliative treatments which use generous margins and where the simplicity of the planning process allows same-day treatment.