1104 / 1542
Delivery uncertainties - IMRT
2%-2 mm
g
for systematic MLC leaf bank shifts
of 0.5, 1, 1.5, and 2 mm. Points that failed in red.
H&N
Prostate
Betzel GT et al, Med Phys 39(10) 2012
Dosimetric effects of delivery
uncertainties in
dose rate
,
gantry angle
, and
MLC leaf
positions
for RapidArc vs sliding
window IMRT plans
how intensity modulation is achieved?
•
sliding window
→
larger number of
overlapping segments and MU
•
RapidArc
→
rotation
→
larger
apertures and less MU
The susceptibility to MLC leaf position
errors is inversely proportional to the
mean leaf gap width
Geometric errors in smaller apertures
→
larger impact on dosimetric errors.