The Role of In-Room kV X-Ray
Imaging for Patient Setup and
Target Localization (TG104)
John Wong (jwong35@jhmi.edu)
David Jaffray (David.Jaffray@rmp.uhn.on.ca)
Fang-Fang Yin (fangfang.yin@duke.edu)
AAPM 20010
Report and Members of TG 104
Fang-Fang Yin, Co-Chair
John Wong, Co-Chair
James Balter
Stanley Benedict
Jean-Pierre Bissonnette
Timothy Craig
Lei Dong
David Jaffray
Steve Jiang
Siyong Kim
Charlie Ma
Martin Murphy
Peter Munro
Timothy Solberg
Q. Jackie Wu
http://www.aapm.org/pubs/reports/RPT_104.pdf
Charges of TG 104
a) Review the current existing kV x-ray systems used in
the radiation treatment room, including system
configurations, specifications, operation principles,
and functionality
b) Discuss the current clinical application methods
about how these systems could be used to improve
treatment accuracy and their limitations.
c) Discuss issues related to effective implementation in
the routine clinical procedures
d) Discuss issues related to acceptance testing and
quality assurance
Objectives
• Understand the current existing kV x-ray systems used
in the radiation treatment room, including system
configurations, specifications, operation principles, and
functionality
• Understand the principles and challenges for treatment
verification
• Understand current clinical application methods about
how these systems could be used to improve treatment
accuracy and their limitations
• Understand issues related to effective implementation of
IGRT in the routine clinical procedures as well as quality
assurance
Commercially Available Systems for In-Room kV Imaging
Outlines
• Overview of the principles and challenges for
treatment verification and image guidance
• Description, applications, and performance
for CT-based systems
• Description, applications, performance, and
QA for in-room projection based systems
• Future development
2-D/3-D In-room Image-Guidance
• On-line systems
• Ceiling/floor-mounted system
• Gantry-mounted system
• On-line techniques
•
•
•
•
Real time 2-D radiographic imaging
Real time 2-D fluoroscopic imaging
2-D to 3-D image fusion
Automatic patient/beam positioning
2-D MV Film and CR Imaging
Off-line 2-D radiographic imaging
Ceiling/Floor-Mounted System
Cyberknife system
X-ray tube
X-ray tube
Detector
Recessed Detector
Detectors under the floor
Detectors above the floor
Curtsey of Accuray, Inc.
Ceiling/Floor-Mounted System
Novalis
system
SDD: 3.62 m
SID: 2.34 m
Pixel: 0.4 mm
Matrix: 512x512
Digital
Detector
kV x-ray
tube
F-F Yin Med Phy 2002
Gantry-Mounted System
Hybrid Image-Guidance System
NovalisTx
System
Duke University
Medical Center
KV Detector
Video/IR Camera
OBI KV
Detector
OBI KV tube
MV Detector
Recessed ExactTract
KV tube
X-ray Imaging in Proton Treatment
Courtesy of Loma Linda University
Courtesy of Heidleberg
University
On-Line In-room Image-Guidance
Patient planning information/
Patient information system
Patient setup
In-room imaging I
Reference images
On-board images
Correction?
Y
In-room imaging III
In-room imaging II
Feedback
Correct position
N
Treatment
2-D vs. 3-D In-room Image-Guidance
• 2-D opportunities
•
•
•
•
•
Efficient and reliable
Fluoroscopic imaging
Imaging during treatment
Low dose
2D to 2D or 2D to 3D image fusion
• 2-D challenges
• Volume information when deformable
• Critical organ information
• Target may not visible
2-D Imaging: MV/MV Isocenter Check
Reference image
Portal image
2-D Imaging: kV/kV Isocenter Check
Image-Guidance with 6D ExacTrac
6D Robotics
Frameless
Radiosurgery
Adaptive Gating
Courtesy of brainlab
Use Case: Intra-fraction Imaging
Example of dual x-ray imaging
Liver - Effect of Breath-Hold
Verification of Gating Windows –
Fluoroscopic Imaging
Fluoroscopic Imaging to verify
gating window for respiratory
gated treatment using onboard imager.
Gating window
Implanted marker
Image-Guided Implementation
• Identification of a Suitable Imaging Technology
• Design, Implementation and Maintenance
– Image Performance and Objectives
– Image Acquisition
– Analysis Tools
•
•
•
•
On-line and Off-line Strategies
Margins, Accuracy, and Precision
Decision-Making and Intervention
Quality Assurance Program for Image-Guided
Processes
• Imaging Dose Considerations
• Manpower and Training
Acceptance Testing: Imaging System
• Room design and shielding consideration
• Verification of Imaging System Installation
• Safety and Mechanical Configurations
• Geometric Calibration
• Localization Accuracy
• Image Quality
• Baseline for routine QA
Commissioning: Imaging System
• Experimentally determine imaging parameters
for optimal image quality and localization
accuracy for different anatomical sites
• Identify potential limitations of the imaging
system
• Setup and document operation procedures for
different localization purposes
Quality Assurance Programs
•
•
•
•
•
Safety and functionality
Geometric accuracy
Dosimetric information
Software and hardware
Imaging system with delivery system
alignment/coincidence
• Image quality
• TG 142 sets the frequencies and criteria
Daily QA Testing
• Collision interlocks
• Imaging and treatment
coordinate coincidence
(1 gantry angle)
• Positioning/repositioning
Alignment of Treatment and
Imaging Coordinate Systems:
Example of calibration
phantoms for ExacTrac system
Daily QA – kV/MV 2D Imaging Test
AP MV
RLat KV
S
S
L
R
I
A
P
I
Imaging Fusion
Software Test
Monthly QA: Monthly QA Tests
• Imaging and treatment
coordinate coincidence
(4 gantry angles)
• Scaling
• Geometric distortion
• Spatial linearity
• Image quality
–
–
–
–
Spatial linearity
Spatial resolution
Contrast
Uniformity and noise
Mechanical checking: Align
the center of the detector
Monthly QA: Geometric Alignment
per Gantry Rotation
S
L
S
R
I
G270 PA
P
S
A
I
G0 Rt
R
S
L
I
G90 AP
A
P
I
G180 Lt
Monthly QA: Scaling Check
Circuit-board
Monthly QA: Image Quality QA for OBI
MVD
Image for QA analysis
CT number
check for CBCT
Annual QA: kV Beam Quality/Energy/Dose
• Unfors Xi
• Fluoro (~5sec)
• Radiography (single-pulse
half-resolution)
• Measurements
• mA, ms, and exposure rate
(R/min) for fluoro, exposure
(mR) for radiography
• kVp and mm (Al HVL).
• Variation from baselines
New Development
•
•
•
•
•
CBCT with a Mobile CT
Dual X-Ray Tubes with Dual Detectors
kV and MV Dual-Energy Imaging
Digital Tomosynthesis
Functional imaging
CBCT with a Mobile C-Arm System
Challenge:
How to correlate
imaging coordinate
with treatment unit
coordinate
C-arm system
www.Siemens.com
In-Line kVision Image-Guidance
System
Proposed ARtISTE system by
Siemens
The kV x-ray axis is in
parallel and coincident to
the treatment beam but at
the opposite direction
Radiographic
Fluoroscopic imaging
kV CBCT
Courtesy of Siemens
Dual X-Ray Tubes with Dual Detectors
Integrated
radiotherapy
imaging system
(IRIS): design
considerations of
tumour tracking
with linac gantrymounted diagnostic
x-ray systems with
flat-panel detectors
Berbeco et al
Phys. Med. Biol. 2004
A New Hybrid Image-Guided
Radiotherapy System
KAMINO et al, IJROBP 2006
Courtesy of Dirk Verellen, Belgium
DTS Imaging Fundamentals
Slice # 1
Slice # 2
1
2
3
4
5
Slice # 3
Slice # 4
Scan angle
Slice # 5
Patient
On-Board 4D-DTS Imaging
30-degree
gantry
rotation
Maurer et al AAPM 2009
DTS with Prior 3D Image Data
CBCT:360o
CT-360o
Deform
Map
CBCT:60o
Ren et al
Med Phys June 2008
kV/MV Dual-Beam CBCT Images
kV+MV CBCT
Diag CT
Yin et al.
Med Phys 2005
Zheng et al 2007
MV-CBCT
kV-CBCT
Soft Tissue Surrogate Imaging: MRI
PTV
Onboard verification
50% isodose line
Under development (MR + Co-60)
Renaissance™ System 1000
www.viewray.com
Verifying Tx
isodose line
relative to PTV
PlanCT  CBCTMRPTV
Opportunity: 4-D MRI Imaging
More than 1 breath cycle
Low dose
Duke University
Onboard Functional Imaging
Active development of
on-board PRT and
SPECT imaging
systems which use
emission kV photons.
On Board Imaging for On-line ART
Daily CBCT
Define anatomy
-of-the-day
Current development:
overall time ~ 5 minutes
Planning CT &
Original Plan
Fast reOptimization
Delivery
A
R
T
Deformable
registration
Plan
Evaluation
Dose
accumulation
dMLC
sequencer
Wu et al PMB 2008
Summary
The introduction of in-room kV imaging provides new
opportunities to further improve treatment accuracy and
precision. At the same time, it presents new challenges for
its efficient and effective implementation.
Each in-room kV imaging method has its strengths and
limitations. The user is well advised to match the clinical
objective with the appropriate technology; or at least to
apply the image guidance information to within the bounds
of its validity.
Summary
Implementation of an in-room kV imaging technology
requires rigorous characterization and validation of its
performance.
Quality assurance measures with phantoms are requisite.
Expertise must be developed and must be re-established
from time to time. One must also be cognizant that in actual
clinical practice, inherent uncertainties of the guidance
solution exist, as each technique has its own range of
uncertainties.
Summary
There is uncertainty in the strength of the surrogate
information as in the case of implanted fiducials; in the
integrity of the information with time as in the case of CT
guidance; and in the residual error related to the
implementation of the correction.
In-room kV guidance clearly offers great potential of
improving treatment accuracy. The promise of in-room kV
guidance can only be realized with a radiation community
that applied the technology with discipline.
Acknowledgements:
Some research works are partially
supported by grants from NIH, Varian
Medical Systems, and GE Health Care.
Thank you for your attention.