Previous Page  635 / 1245 Next Page
Information
Show Menu
Previous Page 635 / 1245 Next Page
Page Background

potential inconsistency between dose calculations and delivery

The difference in radiation field edge and leaf tip position varies with off-axis location

isocenter plane

Source

plane

x

x

HVL

x

w

-10 -7.5 -5 -2.5

2.5 5 7.5 10

-0.2

-0.15

-0.1

-0.05

0.05

0.1

x

cm

cm

x

HVL

- x

w

Delivery (linac):

lookup table or parameterized correction to set leaf position

TPS

:

same method as used for delivery;

or

based on direct calculation of 50% transmission

From Anders Ahnesjö

Modelling the MLC leaf ends