Dose Course Book

1474-1475 / 2239

Dose per MU formalisms: factor-based dose calculations
Irregular fields shaped with MLCs
• MLC design and position in linac head
o Lower jaw replacement
o Upper jaw replacement 1.060
1.080
o Add-on (3rd level) configuration
• Depending of the MLC design, its influence on
Sc and Sp needs to be considered separately:
• Upper or lower jaw replacement MLC
(e.g. Elekta, Siemens linacs)
The equivalent square from a sector
0.920
0.940
0.960
0.980
1.000
1.020
1.040
0 5 10 15 20 25 30 35 40 45
SQUARE FIELD SIZE [cm]
OUTPUT RATIO IN AIR
Primus
GE 43
SL 25
MM 50
Cl 2300 CD
intergration of the MLC aperture is
used for both Sc and Sp
• Add-on (3rd level) configuration (eg Varian
linacs)
Sc ⇐ eq. Sq. of secondary jaws
Sp ⇐ eq. Sq. from MLC aperture
Klein et al 1995 IJROBP
Boyer 1992 MP
Palta et al 1995 MP
Das et al 1999 MP
Georg et al 1999 PMB