Planning techniques Flashcards
1
Q
Details of a fixed FSD..
A
- 100 CM distance from source to skin
- Field size displayed on skins surface
2
Q
Details of SAD..
A
PTV is isocentre
gantry rotates
3
Q
What happens when you make the field size smaller?
A
the monitor units increase and their is more depth dose fall off.
4
Q
How do you make a beam more homogenous?
A
Add wedges / MLC’s
5
Q
What happens to the dose when the prescription dose is at the isocenter?
A
you get more than 100% of dose
6
Q
What do you treat with palliative single field?
A
-prescription at isocenter, so higher max dose and higher minimum dose cover
7
Q
Whats the difference between 6 MV and 10MV?
A
6 mv provides more monitor units
10mv has less entrance dose and is more penetrating
8
Q
Why would you reduce beam weightings?
A
to reduce the dose to certain tissues in a certain location
