1. ROTATION
5:
TPS
MODELING
AND
BEAM
COMMISSIONING
at
UIHC
Radia9on
Oncology
Mentors:
John
Bayouth,
Ph.D.
(04/23/09
–
06/11/09)
By
Vibha
Chaswal

2. Goals
• Model
1
photon
beam
-­‐
Know
parameters
and
their
effects
• Model
1
electron
beam
-­‐
Know
parameters
and
their
effect
• Model
Wedges
• Validate
the
beams
modeled
• Understand
the
nuances
of
TPS
modeling

3. Photon
beams:
data
requirements
• Pdds
• Profiles
• Calibra9on
output
factor
• Rela9ve
output
factors
Data
For
Valida9on!
-­‐ A
subset
of
above
-­‐ Sc
and
Sp
-­‐ Dosimetric
tests,
match
computed
and
measured
dose
distribu9ons

4. Data
collected
for
assumed
clinical
applica9on

5. TPS
modeling:
The
Machine

6. TPS
Modeling:
The
machine

7. TPS
Modeling:
The
Radia9on
Beam
• Fine
tuning
Profiles
-­‐
Effec9ve
source
size
for
Penumbra
matching
-­‐ Gaussian
width
and
height
of
FF
scacer
source
for
tails
-­‐ Transmission
factors
of
Jaw
and
MLC
for
tails
region

8. Energy
Spectrum

9. Energy
Spectrum:
Build-­‐up
region

10. In-­‐field
Region:
FF
acenua9on
using
cone
model
With
Off-­‐axis
Soeening
factor

11. In-­‐field
Region:
FF
acenua9on
using
arbitrary
profile
With
Off-­‐axis
Soeening
factor

12. Off-­‐axis
soeening

13. Out-­‐of
field
regions:
Penumbra
and
tails

14. Out-­‐of
field
modeling
parameters

15. Beam
Valida9on:
PDDs
Result:
All
Pdds
pass
within
2%
or
2mm

16. Beam
Valida9on:
Profiles
Result:
Within
3%
or
3mm
except
outliers
in
tail
regions

17. Beam
Valida9on
tests:
MU
verifica9on

18. Beam
valida9on:
R
and
V
import

19. Rela9ve
Decision
Maps:
error
Limit
=
3
%,
dta
Limit
=
3
mm

20. TPS
Modeling:
The
machine,
Collimator
rota9on
incorrect

21. Electron
beams:
Data
required

22. Electron
Beam
Parameters

23. Two
adjustable
parameters
- Off-axis ratios, and
- The scatter correction
factor (FMCS), dose
spread out in media
relative to air.

24. Electron
Beam
modeling

25. Electron
PDD

26. Thank
you!!!!!