PLANNING

Question 1

GROSS TUMOUR VOLUME (GTV)

Answer 1

The gross palpable or visable/demonstrable extent and location of malignant growth.

DEF: Is usually the disease volume which is clearly definable or thich can be recorded and mesadured using imagining modalities.

Question 2

Clinical Target Volume (CTV)

Answer 2

DEF: The tissue volume that contains a demontrable GTV and/or sub-clinical microscopic malignant disease, which has to be eliminated. This volume thus has to be treated adequatley in order to achieve the aim of theraphy, cure or palliation.

Question 3

Internal Target Volume (ITV):

Answer 3

This is defined as the volume containing the CTV plus an internal margin.

Question 4

Planning target volume (PTV)

Answer 4

The planning target volume is a geometrical concept, and it is defined to select appropriate beam arrangements, taking into consideration the net effect of all possible geometrical variations, in order to ensure that the prescribed dose is actually absordeb in the CTV

Question 5

Organ at risk (OAR)

Answer 5

Organ at risk is defined as an organ whose sensitivity to radiation is such that the dose received from a treatment plan may be significant compared to its tolerance, possibly requiring a change in the beam arrangement or a change in the dose.

Question 6

Treated Volume (VT)

Answer 6

The TV is the volume of tissue enclosed within a specific isodose envelope, with the absorbed dose specified by the radiation oncology team as appropriate to achieve tumor erradication or palliation, within the bounds of accepatable complicactions.

Question 7

Irradiated Volume

Answer 7

It is defined as the volume that receives a dose considered significant in relation to normal tissue tolerance.

Question 8

Hot Spot

Answer 8

It is defined as a volume > 15mm in minium diameter outside the PTV that receives more than 105% of the specified PTV dose.

Question 9

Internal Margin (IM)

Answer 9

It is situated around CTV or organ at risk and accounts for the uncertainities in contouring of the organs and target volume and uncertainities caused by a physiologic movements and(or changes of shapes and size of the CTV and RV in relation to reference points.

Question 10

Internal Risk Volume (IRV)

Answer 10

It is defined by the outer boundry of the volume of organ at risk (IRV)

Question 11

Reamaining Volume at Risk (RVR)

Answer 11

Is the imaged volume within the patient, excluding any deliniated OAR and the CTV, and is defined by the difference between the vlume enclosed by the external contour of the patient and that of the CTV and OAR on the slices that have been imaged.