Table 1: Definition of volumes in radiotherapy.

Gross tumour volume
(GTV)
The gross, palpable, or visible/clinically demonstrable location and extent of the malignant growth

Clinical target volume
(CTV)
Anatomical concept-defines a tissue volume that contains a GTV and/or subclinical microscopic malignant disease, which has to be eliminated.

Planning target volume
(PTV)
Geometrical concept-selects appropriate beam sizes and arrangements, while taking into account all the possible geometrical variations and inaccuracies.