|Definitions of target volumes according to ICRU (International Commission on Radiation Units and Measurements)
|CTV (Clinical Target Volume)
||Tissue volume that contains a GTV and/or subclinical microscopic malignant disease, which has to be eliminated.
|ITV (Internal Target Volume)
||Volume encompassing the CTV and IM. (ITV = CTV + IM)
|PTV (Planning Target Volume)
||Geometrical concept. Defined to select appropriate beam sizes and beam arrangements, taking into consideration the net effect of all the possible geometrical variations and inaccuracies in order to ensure that the prescribed dose is actually absorbed in the CTV. Its size and shape depend on the CTV but also on the treatment technique used, to compensate for the effects of organ and patient movement, and inaccuracies in beam and patient setup.
|OAR (Organ at Risk)
||Normal tissues whose radiation sensitivity may significantly influence treatment planning and/or prescribed dose.
|PRV (Planning Organ at Risk Volume)
||Includes margin around the OAR to compensate for changes in shape and internal movement and for set-up variation.
|TV (Treated Volume)
||Volume enclosed by an isodose surface.
|IV (Irradiated Volume)
||The volume that receives a dose that is significant in relation to normal tissue tolerance.
|CI (Conformity Index)
||Relationship between TV and PTV (TV/PTV).
Lateral tumors are located on the cheek, gum, and retromolar space with 1 cm distance to the midline without spreading to contralateral lymph nodes. In these cases, a treatment technique can be utilized to reduce the dose absorbed by healthy tissue of the oral cavity and neck. Tongue cancer and tumors growing into tongue muscle should always, regardless of localization, be treated as a midline tumor.
Midline tumors are located on the tongue, floor of the mouth, and hard palate.
These tumors and tumors reaching these regions that originate in the cheek and gum have a tendency to metastasize bilaterally. Malignant cells can spread with lymph drainage from the anterior tongue directly to midjugular and supraclavicular lymph nodes.