Disclosure
AAPM 2011
Act
Act III
II
Planning
Delivery
Image Processing
for
T
Tx
Delivery
x Planning
Jan-Jakob
Marc Kessler
Sonke
Netherlands
The University
Cancer
of Michigan
Institute
Radiotherapy Procedure
Act III:
Align patient on
machine on tattoos and
treat (many days)
Act I:
Tattoo, align and
scan patient
Act II:
Define the target
and design a
treatment plan
• Our department has research contracts with:
• Elekta Oncology Systems
• Philips Radiation Oncology Systems
• Siemens Medical Solutions
• Our department licenses software to:
• Elekta Oncology Systems
Setup Errors
The patient moves from day to day
1
Organ Motion
How can we solve this problem ?
Organs move
from day to day
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
Safety Margins
• 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
Verellen et al. Nature Reviews Cancer 2007
2
Many In-room Imaging Systems
Visualization
Visualization: Image Fusion
Reference Image
Visualization: Sliding Window
Localization Image
3
Visualization: Overlay
Complementary color overlay clearly shows gross differences and local
differences provided adequate contrast
Bone Registration
Visualization: Animation
Animation clearly shows local changes
Bone Registration
4
Pop Quiz
What is the purpose of IGRT
19%
20%
20%
21%
20%
1.
2.
3.
4.
5.
Make pretty images
Minimize setup errors
Quantify organ motion
Reduce PTV margins
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
Electronic Portal Imaging
2D Image Guidance
5
Portal Image Quality
Preprocessing: unsharp masking
Image quality is limited by:
• Projective nature of 2D
images
A-P
• Low DQE of EPIDs in MV
range
• Limited dose used for
imaging (ALARA)
Lat
.
Prostate
• Limited contrast differences
of tissue in the MV range
Lung
Mostly limited to bony anatomy alignment
minimizing setup errors
Top-hat transform
Portal image analysis - 2D
Reference image Match field-edge Match anatomy
Original image
Binary top-hat enhanced image
 Setup Error = Anatomy Match – Field-Edge Match
6
3D EPID Dose reconstruction
prostate VMAT plan
3D Image Guidance
EPID movie
• Energy: 10 MV
• 243 frames
• delivery time: 96 s
Dose per frame
Accumulated dose
axial slice through isocentre
Jean-Pierre Bissonnette: PMH
MV/kV Coincidence
Jean-Pierre Bissonnette: PMH
kV/MV Calibration Concept
BB (reconstruction
Isocentre)
MV mechanical
isocentre
kV
y
• Treatment and
imaging beams are
orthogonal
MV radiation isocentre
x
Calibrated isocentre
z
7
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)
+1mm
qgantry
qgantry
u
-1mm
-180
v
qgantry
Jean-Pierre Bissonnette: PMH
1. MV Localization (0o) of BB; collimator
at 0 and 90o.
Geometry: Flex calibration
+180
Reconstruction
4. Measure BB Location in kV
radiographic coordinates (u,v) vs. q gantry.
5. Analysis of ‘Flex Map’ and Storage for
Future Use.
6. Employment of ‘Flex Map’ During
Routine Clinical Imaging.
MV Flex
kV Flex
Geometry: Flex calibration
0.5
0.4
displacement [cm]
0.3
0.2
0.1
0
-0.1
X
Y
-0.2
-200
MV Flex
kV Flex
-150
-100
-50
0
50
G
G
100
(AB)
(GT)
150
200
°
angle [ ]
8
Marc Kessler / UM
Geometric non-idealities (Flex)
How many Degrees of Freedom?
PET/CT
2 mm panel shift
Correctly Calibrated
Requirements for IGRT
registration
MR - CT
4D CT
0?
3 to 6
3xN
None ?
Few
Many
Automatic matching on region of
interest built-in in Synergy system
reference
localization
reference
localization
• 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
Tumor in top of neck
Required table shift:
(-3.2, -1.5, -0.6) mm
Tumor in lower part of neck
Required table shift:
(+1.5, -3.2, -6.1) mm
9
Rotations
Rotations
Correction by Couch Shift
Modify Rotation Point
10
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)
Pop Quiz
How many degrees of freedom are typically used
for IGRT image registration
Cone beam CT
10 CBCT scans: automatic bone match
24%
20%
23%
16%
17%
Planning CT contours
placed automatically
1.
2.
3.
4.
5.
0
3
6
42
Not enough
10 CBCT scans: automatic prostate match
help line (GTV+3.6 mm)
Smitsmans et al., IJROBP 2004, 2005
11
Martin LaChaine: Elekta
Ultrasound Guided RT (Clarity™)
Pop Quiz
Clarity Sim
How many degrees of freedom are typically used
for IGRT image registration
a) 0
b) 3
c) 6
d) 42
e) Not enough
Clarity AFC Workstation
Clarity Guide
Throughout Radiation Oncology Care Cycle
Sim
Frank Verhaegen: Maastro
Correct Answer: c)
Van Herk et al. Seminars in Radiation Oncology, 2007
Linac
Frank Verhaegen: Maastro
3DUS vs CT for breast seroma cavity
Planning CT
Daily US
Fusion
12
Radiotherapy systems with
integrated MRI
1.5 T MRI accelerator for MRI guided RT
at UMC Utrecht
Bas Raaymakers: UMC
Prototype MRI accelerator
MRI-Linac Utrecht
Courtesy of Bas Raaijmaakers
MRI-Co60 ViewRay
Courtesy of Jim Dempsey
No impact of beam on MRI
Bas Raaymakers: UMC
Inter- and intra- fracation motion of cervix
4D Image Guidance
Day to day variation
13
Breathing
Respiratory signal extraction
Vertical
derivative filter
Horizontal
projection
Temporal
concatenation
[Zijp, ICCR, 2004]
[van Herk, ICCR, 2007]
Amsterdam shroud (2D image)
RCCBCT
3D versus 4D CBCT
• 4D Data set
• 8 x 84
projections
• 3D Data set
• 670 projections
14
ROI by GTV Expansion
4D CBCT + GTV Contour
Local Rigid Body Registration
Visual Validation
15
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)
2 cm
9 mm margin is adequate even with 2 cm intrafraction motion
16
Jim Dempsey / ViewRay
Bas Raaymakers: UMC
1D MRI, Navigator echos (NE)
15 ms per acquisition
1D MRI signal
4D Liver MRI
Time
Monitoring breathing at superior
side of liver
Bas Raaymakers: UMC
• In diagnostics
used to track/gate
respiration
• Imaging stack is
moved according
to NE signal
• Diaphragm
monitored
• Can be positioned
anywhere in any
orientation
Bas Raaymakers: UMC
1D MRI navigators, monitoring breath hold
stability and on-set of breathing
Gated radiation on moving cart
•
Cart in scanner bore, moving along FH-direction
•
Motion by electric motor/crankshaft mechanism
•
Radiation sensitive film to record dose
•
Water phantom to track position
•
5x5 cm2 radiation beam, dose ~2Gy, in static situation T = 2.5 min.
1D MRI signal
• Sinusoidal/respiratory-like motion
Time
Monitoring breath hold at inferior
side of liver
17
Bas Raaymakers: UMC
Gated radiation delivery
Pop Quiz
Which motion management strategy has the
largest impact on the delivered dose:
18%
22%
20%
20%
20%
1.
2.
3.
4.
5.
4D Imaging
4D Planning
4D Delivery
4D Image Guidance
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
Adaptive Radiotherapy
Correct Answer: d)
Guckenberger et al. Radiother. Oncol. 2009
18
Differential Variability
Repeat 4D cone beam CT
No couch correction can solve this problem
Shows respiration, tumor shrinkage and baseline position variation
Fraction at day # 36
Anatomical Changes
Bony anatomy
registration
non-rigid registration
19
Results, volume change of target + OAR
Deformable Registration
Relative weight loss, neck radius and delineated volumes
1.10
1.00
CTV
PTV
Brain stem
Left parotid
Spinal cord
Oral Cavity
1
Neck
0.80
0.8
weight
0.70
CTV
Volume [%]
units
0.90
PTV tot
0.60
Spinal cord
Parotid Li
0.50
Parotid Re
0.40
0
5
10
15
20
25
30
35
40
0.6
0.4
treatment day
day
0
1
7
14
21
28
36
CTV
387
381
378
373
373
344
315
PTV
1051
1036
1035
1008
1012
969
916
Spinal cord
20
20
20
20
20
21
20
Parotid Li
31
31
32
27
28
23
18
Parotid Re
21
21
21
20
19
17
15
t(s)
67
120
104
55
141
155
0.2
0
0
Pre-treatment
Applications – dose painting
0.4
0.6
0.8
Dose [% Dmax]
1
1.2
1.4
Summary
• Geometrical uncertainties limit the precision of
radiotherapy
Prescription function
Treatment response
Mid-treatment
0.2
• 2D,3D&4D image registration and guidance
increases the precision of RT allowing margin
reduction and dose escalation
• Adaptive RT further individualized treatment
delivery
Robert Jeraj / UW
20
Acknowledgements
Marcel van Herk
Peter Remeijer
Jochem Wolthaus
Simon van Kranen
Simon Rit
Monique Smitsmans
Anton Mans
David Jaffray
Doug Mosely
Marc Kessler
Jean-Pierre Bissonnette
Robert Jeray
Frank Verhaegen
Bas Raaymakers
Jim Dempsey
Martin LaChaine
21