Principles of radiotherapy 2

Question 1

what does increasing the FSD do?

Answer 1

Increases beam penetration

decreases dose rate

increases relative %DD

Question 2

why do we need to modofy beam intensity?

Answer 2

to create homogenous dose dis

to account for:
- shape of patient
- missing tissue
- how multiple treatment beams interact with each other
- different absorption patterns in different tissues
- differences in isodose dose patterns of fields

Question 3

what is tissue equivalent material

Answer 3

absorbs or scatters radiation in a similar way to human tissue

uses in:
skin treatments
lip tumours
sarcomas
breast scars

Question 4

what is TEM used as bolus?

Answer 4

placed on patient, not fully covering beam entry

adapts dose dis to achieve uniform delivery

Question 5

what is TEM used as Build up

Answer 5

placed on patient on the surface where the beam enters to increase dose to skin

Question 6

what does a bolus do?

Answer 6

conpensate for missing tissue

skin sparing effect lost and patient skin reaction really bad