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1
Marc Kessler
The University of Michigan
Image Processing
for
Tx Planning
Act II
Planning
Jan-Jakob Sonke
Netherlands Cancer Institute
Image Processing
for
Tx Delivery
Act III
Delivery
AAPM 2011
Disclosure
• Our department has research contracts with:
• Elekta Oncology Systems
• Philips Radiation Oncology Systems
• Siemens Medical Solutions
• Our department licenses software to:
• Elekta Oncology Systems
Radiotherapy ProcedureAct I:
Tattoo, align and
scan patient
Act II:
Define the target
and design a
treatment plan
Act III:
Align patient on
machine on tattoos and
treat (many days)
Setup Errors
The patient moves from day to day
2
Organs move
from day to day
Organ Motion How can we solve this problem ?
1. Use large margins, irradiating
too much healthy tissues
2. Use small margins, and risk
missing the target
3. Or: use image guided radiotherapy
Image Guided Radiotherapy
• Image the tumor + organs-at-risk or their
surrogates just prior or during treatment
• Assess changes in patient position relative to
treatment plan
• Adapt treatment plan (couch shift) to account for
changes, increasing treatment precision
Safety Margins
Verellen et al. Nature Reviews Cancer 2007
3
Many In-room Imaging Systems
Visualization
Visualization: Image Fusion
Reference Image Localization Image
Visualization: Sliding Window
4
Visualization: Overlay
Complementary color overlay clearly shows gross differences and local
differences provided adequate contrast
Visualization: Animation
Animation clearly shows local changes
Bone Registration Bone Registration
5
Pop Quiz
What is the purpose of IGRT
20%
21%
20%
20%
19% 1. Make pretty images
2. Minimize setup errors
3. Quantify organ motion
4. Reduce PTV margins
5. Sell more expensive treatment machines
Pop Quiz
What is the purpose of IGRT
a) Make pretty images
b) Minimize setup errors
c) Quantify organ motion
d) Reduce PTV margins
e) Sell more expensive treatment machines
Correct Answer: d)
Seminars in Radiation Oncology Volume 17, Issue 4
2D Image Guidance
Electronic Portal Imaging
6
Portal Image QualityImage quality is limited by:
• Projective nature of 2D
images
• Low DQE of EPIDs in MV
range
• Limited dose used for
imaging (ALARA)
• Limited contrast differences
of tissue in the MV range
Mostly limited to bony anatomy alignment
minimizing setup errors
Prostate Lung
A-P
Lat
.
Preprocessing: unsharp masking
Top-hat transform
Original image Binary top-hat enhanced image
Portal image analysis - 2D
Match field-edge Match anatomyReference image
Setup Error = Anatomy Match – Field-Edge Match
7
3D EPID Dose reconstruction
prostate VMAT plan
• Energy: 10 MV
• 243 frames
• delivery time: 96 s
EPID movie Dose per frame Accumulated dose
axial slice through isocentre
3D Image Guidance
MV/kV Coincidence
• Treatment and
imaging beams are
orthogonal
Jean-Pierre Bissonnette: PMH
kV/MV Calibration Concept
kV
BB (reconstruction
Isocentre)
MV radiation isocentre
MV mechanical
isocentre
x
y
z
Calibrated isocentre
Jean-Pierre Bissonnette: PMH
8
qgantry
4. Measure BB Location in kV
radiographic coordinates (u,v) vs. qgantry.
+180qgantry-180
u
v
5. Analysis of ‘Flex Map’ and Storage for
Future Use.
+1mm
-1mm
Reconstruction
qgantry
6. Employment of ‘Flex Map’ During
Routine Clinical Imaging.
1. MV Localization (0o) of BB; collimator
at 0 and 90o.
2. Repeat MV Localization of BB for
gantry angles of 90o, 180o, and 270o.
3. Analyze images and adjust BB to
Treatment Isocentre (± 0.3 mm)
Jea
n-P
ierr
e B
isso
nn
ett
e:
PM
H
Geometry: Flex calibration
MV Flex kV Flex
Geometry: Flex calibration
MV Flex kV Flex-200 -150 -100 -50 0 50 100 150 200
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
angle [°]
dis
pla
cem
en
t [c
m]
XG
(AB)
YG
(GT)
9
Geometric non-idealities (Flex)
2 mm panel shift Correctly Calibrated
How many Degrees of Freedom?
Few ManyNone ?
PET/CT MR - CT 4D CT
3 x N3 to 60 ?
Marc Kessler / UM
Requirements for IGRT
registration
• Fast and robust image registration
• Easy visual validation
• Registration result drives a couch shift
Rigid registration with 6 degrees of freedom is
a likely candidate
Automatic matching on region of
interest built-in in Synergy system
Tumor in top of neck Tumor in lower part of neckRequired table shift:
(-3.2, -1.5, -0.6) mmRequired table shift:
(+1.5, -3.2, -6.1) mm
reference localization reference localization
10
Rotations Rotations
Correction by Couch Shift Modify Rotation Point
11
Correction by Couch Shift Soft Tissue Guidance
Grey-value registration TAP / TCC / TLR / RAP / RCC / RLR
** Smitsmans et al.,
IJROBP 60 (2004)
Automatic prostate localization in CBCT (30 s)
Cone beam CT
Planning CT contours
placed automatically
10 CBCT scans: automatic bone match
10 CBCT scans: automatic prostate match
help line (GTV+3.6 mm)
Smitsmans et al., IJROBP 2004, 2005
Pop Quiz
How many degrees of freedom are typically used
for IGRT image registration
17%
16%
23%
20%
24% 1. 0
2. 3
3. 6
4. 42
5. Not enough
12
Pop Quiz
How many degrees of freedom are typically used
for IGRT image registration
a) 0
b) 3
c) 6
d) 42
e) Not enough
Correct Answer: c)
Van Herk et al. Seminars in Radiation Oncology, 2007
Clarity Sim
Ultrasound Guided RT (Clarity™)
Throughout Radiation Oncology Care Cycle
LinacSim
Clarity AFC Workstation Clarity Guide
Martin LaChaine: Elekta
Fra
nk
Ve
rha
eg
en
: M
aa
str
o
3DUS vs CT for breast seroma cavity
Frank Verhaegen: Maastro
Planning CT Daily US Fusion
13
Radiotherapy systems with
integrated MRI
MRI-Linac Utrecht
Courtesy of Bas Raaijmaakers
MRI-Co60 ViewRay
Courtesy of Jim Dempsey
1.5 T MRI accelerator for MRI guided RT
at UMC Utrecht
No impact of beam on MRI
Prototype MRI accelerator
Bas Raaymakers: UMC
Inter- and intra- fracation motion of cervix
Day to day variation
Bas Raaymakers: UMC
4D Image Guidance
14
Breathing Respiratory signal extraction
Vertical
derivative filter
Temporal
concatenation
Amsterdam shroud (2D image)
Horizontal
projection
[Zijp, ICCR, 2004]
[van Herk, ICCR, 2007]
RCCBCT 3D versus 4D CBCT
• 4D Data set
• 8 x 84
projections
• 3D Data set
• 670 projections
15
ROI by GTV Expansion 4D CBCT + GTV Contour
Local Rigid Body Registration Visual Validation
16
Apply Correction Impact of Respiratory Motion
on Dose Distribution
Planned distribution Delivered distribution
• Shift of the dose distribution due to
displacement of the mean tumor position
• Blurring of the dose distribution due to
breathing around the mean position
Planned dose distribution:
hypofractionated lung treatment 3x18 Gy
Realized dose distribution with daily IGRT
on tumor (no gating)
9 mm margin is adequate even with 2 cm intrafraction motion
2 cm
17
4D Liver MRIJim Dempsey / ViewRay
1D MRI, Navigator echos (NE)
15 ms per acquisition
Time
1D
MR
I sig
na
l
• In diagnostics
used to track/gate
respiration
• Imaging stack is
moved according
to NE signal
• Diaphragm
monitored
• Can be positioned
anywhere in any
orientationMonitoring breathing at superior
side of liver
Bas Raaymakers: UMC
1D MRI navigators, monitoring breath hold
stability and on-set of breathing
Monitoring breath hold at inferior
side of liver
Time
1D
MR
I sig
na
l
Bas Raaymakers: UMC
Gated radiation on moving cart
• Cart in scanner bore, moving along FH-direction
• Motion by electric motor/crankshaft mechanism
• Sinusoidal/respiratory-like motion
• Radiation sensitive film to record dose
• Water phantom to track position
• 5x5 cm2 radiation beam, dose ~2Gy, in static situation T = 2.5 min.
Bas Raaymakers: UMC
18
Gated radiation delivery
Bas Raaymakers: UMC
Pop Quiz
Which motion management strategy has the
largest impact on the delivered dose:
20%
20%
20%
22%
18% 1. 4D Imaging
2. 4D Planning
3. 4D Delivery
4. 4D Image Guidance
5. The impact of respiration is over exaggerated
Pop Quiz
Which motion management strategy has the
largest impact on the delivered dose:
a) 4D Imaging
b) 4D Planning
c) 4D Delivery
d) 4D Image Guidance
e) The impact of respiration is over exaggerated
Correct Answer: d)
Guckenberger et al. Radiother. Oncol. 2009
Adaptive Radiotherapy
19
Differential Variability
No couch correction can solve this problem
Repeat 4D cone beam CT
Shows respiration, tumor shrinkage and baseline position variation
Anatomical Changes
Bony anatomy
registration
non-rigid registration
Fraction at day # 36
20
Results, volume change of target + OAR
Relative weight loss, neck radius and delineated volumes
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
0 5 10 15 20 25 30 35 40
treatment day
un
its
Neck
weight
CTV
PTV tot
Spinal cord
Parotid Li
Parotid Re
day CTV PTV Spinal cord Parotid Li Parotid Re t(s)
0 387 1051 20 31 21 -
1 381 1036 20 31 21 67
7 378 1035 20 32 21 120
14 373 1008 20 27 20 104
21 373 1012 20 28 19 55
28 344 969 21 23 17 141
36 315 916 20 18 15 155
Deformable Registration
0 0.2 0.4 0.6 0.8 1 1.2 1.40
0.2
0.4
0.6
0.8
1
Dose [% Dmax]
Vo
lum
e [%
]
CTV
PTV
Brain stem
Left parotid
Spinal cord
Oral Cavity
Applications – dose painting
Pre
-tre
atm
en
tM
id-t
rea
tme
nt
Treatment response
Prescription function
Robert Jeraj / UW
Summary
• Geometrical uncertainties limit the precision of
radiotherapy
• 2D,3D&4D image registration and guidance
increases the precision of RT allowing margin
reduction and dose escalation
• Adaptive RT further individualized treatment
delivery
21
Acknowledgements
Marcel van HerkPeter RemeijerJochem WolthausSimon van KranenSimon RitMonique SmitsmansAnton MansDavid JaffrayDoug MoselyMarc KesslerJean-Pierre BissonnetteRobert JerayFrank VerhaegenBas RaaymakersJim DempseyMartin LaChaine