The Netherlands Cancer Institute
Antoni van Leeuwenhoek Hospital
Adaptive Radiotherapy for H&N
Imaging
Disclosure
• Our department has research
contracts with:
• Elekta Oncology Systems
• Philips Radiation Oncology Systems
• Siemens Medical Solutions
Jan-Jakob Sonke
• Our department licenses software to:
• Elekta Oncology Systems
Immobilization
3-Point PetG Mask
IGRT for H&N?
Stereotactic frame
• Setup error minimized trough
immobilization
• No Organ motion
5-Point Aquaplast Mask
• Small margins sufficient
No place for volumetric IGRT?
Cone Beam CT Acquisition
NKI high speed reconstruction software (20 s)
•Courtesy to Doug Moseley, PMH
Sample Image
Beam Hardening
Image analysis: comparison
with reference image
•reference
Online Correction Protocol at NKI
(brain metastasis 1 x 18 Gy)
•localization
• scan patient on machine with CBCT (1 min)
• match to planning scan on bony anatomy and visual
verification (30 sec)
• correct errors larger than 1 mm (1-2 min)
• rescan for verification (1 min)
• treat (5-10 min)
• rescan after treatment (1 min)
Reference image
(planning CT)
Localization image
(cone beam CT)
Mixed image
(not matched)
Match procedure – First scan, not
matched
Match procedure – Pre-treatment
scan
Match procedure – Post-treatment
scan
Results
•
Left-right (mm) Cranial-caudal (mm)
Mean
SD
Mean
SD
Ant-post (mm)
Mean
SD
Before corr.
-0.8
1.5
-0.1
2.3
-0.5
2.0
After corr.
-0.1
0.7
0.1
1.0
-0.1
0.9
Intra frac.
-0.1
0.3
0.1
0.3
-0.1
0.2
X→ +
Random Posture Changes
Large ROI-Registration
• Ambiguous result: inaccurate registration versus deformation
• Large bones dominate registration result
Multi match registration
Multiple region of interest to rigidly register
local anatomy
Results: offline vs online large ROI
Multi match registration
Thin plate spline warp to visualize multiple
registration result in a single view
Results: online (large ROI), mean,
Outliers (error > 5mm)
Outliers (error > 5mm)
# fractions with ‘warning:’
offline large ROI : 368 (64%)
online large ROI : 319 (56%)
# fractions with ‘warning:’
offline large ROI : 368 (64%)
online large ROI : 319 (56%)
mean
: 239 (42%)
574 fractions total
574 fractions total
Adaptive RT Protocol 1
• Random variability converted to a
systematic error during CT simulation
• Image Patients for the first N fractions
• Calculate mean displacements for
relevant regions
• Patients with systematic errors > T
eliagible for adaptive planning
Progressive Anatomy Changes
Progressive Anatomical
Changes
Quantification of progressive
• 2 mm
changes
• 4-7 small implanted markers
•
0.35 mm
• 14 patients with transorally accessable tumors:
• T-Stage
T2
T3
T4
3
7
4
• Radiotherapy:
Radio-chemotherapy:
3
11
• Evaluate centre of mass and individual marker
position variability
COM alinged
on nearby bony anatomy
Example 1
M(cm)
(cm)
(cm)
margin (cm)
LR
-0.01
0.09
0.07
CC
-0.03
0.12
0.12
AP
-0.04
0.17
0.11
0.28
0.39
0.51
M=2.5Σ+0.7σ
Timetrends in COM displacement
Absolute marker positioning uncertainty
absolute marker positioning inaccuracy (vector length)
Timetrend COM displacement
after corrections (cm/day)
LR
CC
AP
0.006
0.003
-0.014
-0.001
-0.008
0.001
0.007
0.000
0.003
0.003
-0.003
-0.001
0.002
-0.007
0.003
-0.006
0.004
-0.002
-0.003
0.012
0.000
-0.002
-0.015
-0.005
0.001
-0.009
-0.008
0.000
0.001
-0.001
0.001
-0.006
0.002
0.000
0.001
-0.003
0.002
0.001
-0.004
-0.004
0.001
0.006
Average
0.007
0.015
0.014
0.45
Group average vector length (cm)
Patient
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
1
13/14 patients significant time trend, p<0.05 (red)
2
3
4
Week #
5
6
7
Deformable registration to asses anatomy changes
Adaptive RT Protocol 2
• Repetitively Image the patients over
the course of treatment
• Quantify geometric errors
• Calculate dosimetric consequences
• Patients with dosimetric deviations
> d eligible for adaptive planning
Anatomy differences: effect on dose
Rigid registration
BSpline registration
Coronal
Sagittal
Example 2: Tissue-to-Tissue Correspondence?
Tissue to tissue correspondence
•2.5 cm
Anatomy changes
different dose at a different place
Dose accumulation:
•
•
New dose distribution
Warp dose back to original anatomy
Deformation field
Conclusions
• Repetitive volumetric imaging reveals
considerable geometric variability over
the course of treatment
• Adaptive plan modification after the
first week of treatment can mitigate
systematic posture differences
• Subsequent adaptive plan modification
have the potential mitigate treatment
response induced progressive
changes
Acknowledgements
Marcel van Herk
Peter Remeijer
Simon van Kranen
Coen Rasch
Angelo Mencarelli
Suzanne van Beek
David Jaffray
Doug Mosely