Volumes, margins and OAR

Question 1

What is outlined by the GTV?

Answer 1

gross tumour volume- visible tumour

Question 2

What is outlined by the CTV?

Answer 2

GTV + uncertainties for microscopic spread

Question 3

What is outlined by the PTV?

Answer 3

Margins around the CTV to account for movement and changes in shape and size

Question 4

What does the PTV include?

Answer 4

Internal margin and set up margin

Question 5

What is the internal margin for?

Answer 5

To account for movement and size variation of organs+ surrounding tissues

Question 6

What is set up margin for?

Answer 6

Account for errors in patient set up

Question 7

What is intra-fraction?

Answer 7

Changed during treatment time

Question 8

What is inter-fraction?

Answer 8

Changes between fractions

Question 9

What is the margin for OAR called?

Answer 9

PRV

Question 10

What are serial organs?

Answer 10

Damage to one part will cause organ failure eg. brainstem, optic nerve

Question 11

What are parallel organs?

Answer 11

Damage to one part will not effect the rest o the organ eg. lung