Update on TG 147: QA for nonradiographic localization and
positioning systems
AAPM Anaheim, CA 2009
Twyla Willoughby
Thank-You
Joerg Lehmann, Ph.D.: TG Co-Chair
Radiological Associates of
Sacramento
José A. Bencomo, Ph.D.
US Oncology
Anil Sethi, Ph.D.
Loyola University Medical Center
Timothy D. Solberg, Ph.D.
UT Southwestern Medical Center
Shirish K. Jani, Ph.D.
Sharp Metropolitan Medical Campus
Wolfgang A. Tomé, Ph.D.
University of Wisconsin
School of Medicine and Public Health
Lakshmi Santanam, Ph.D.
Washington University
Tim Waldron, M.S.
University of Iowa
IGRT
• Ultrasound: Soft tissue alignment – mostly
prostate
• Orthogonal MV x-rays: Bony anatomy or implanted
markers
• Orthogonal kV x-rays: Bony anatomy or implanted
markers
• Cone-beam CT: image quality may be an issue
• MV CT: Image quality may be a concern
• In room CT: Good image quality not exactly same
treatment position
• Other: Video, RF, and laser alignment systems
Disclaimer
• Task Group Report has NOT been
approved as of yet.
• Projected publication date: Late
2009/Early 2010
What is Optical Tracking?
• Optical tracking is a means of determining in real-time the
position of an object by tracking the positions of either
active or passive infrared markers attached to the object.
The position of the point of reflection is determined using a
camera system.
Active markers
Passive markers
Camera
Meeks RSNA 2002
Stereo Correspondence
How Does it Work?
Optical Tracking
Meeks RSNA 2002
Calibration to Isocenter
Meeks RSNA 2002
Vector for
room
coordinates
pi
’
3x3 rotation matrix
Translation vector
=R
pi +
T
Equation can be solved numerically using
optimization algorithms (Hook and Jeeves,
etc.), or closed form solutions such as
single value decomposition or Horn’s
method (quaternions)
Meeks RSNA 2002
Vector for
image
coordinates
Infrared Camera Alignments
Meeks, S.L., et al., Image localization for frameless
stereotactic radiotherapy. Int J Radiat Oncol Biol Phys, 2000.
46(5): p. 1291-9.
Tome, W.A., et al., Optically guided intensity modulated
radiotherapy. Radiother Oncol, 2001. 61(1): p. 33-44.
Other Alignment Systems (VisionRT)
Waldron, T. Univ of Iowa
C-Rad Sentinel™
LAP: Galaxy
Waldron, T. Univ of Iowa
Waldron, T. Univ of Iowa
Video and Laser References
Moore, C., et al., Opto-electronic sensing of body surface topology
changes during radiotherapy for rectal cancer. Int J Radiat Oncol Biol
Phys, 2003. 56(1): p. 248-58.
Schoffel, P.J., et al., Accuracy of a commercial optical 3D surface
imaging system for realignment of patients for radiotherapy of the
thorax. Phys Med Biol, 2007. 52(13): p. 3949-63.
Bert, C., et al., A phantom evaluation of a stereo-vision surface
imaging system for radiotherapy patient setup. Med Phys, 2005. 32(9):
p. 2753-62.
Siebert, Human Body 3D imaging by speckle texture projection
photogrammetry. Sensor Review, 2000. 20(3).
Super Dimension: RF guided
Bronchoscopy
Transponder
tip
Ascension Technology
Ascension Technology products use RF sensors to track the position and orientation in real-time
of instruments including ultrasound probes. Tracking accuracy is unaffected by the nearby presence
of conductive metals including aluminum, titanium and stainless steel 300
Calypso
Medical
System
Resonator
Current
Source
Coil
Current
Excitation
Waveform
Response
Waveform
Excitation
Phase
Ring
Down
Phase
RF References
Wagner, A., et al., Quantitative analysis of factors affecting intraoperative precision and
stability of optoelectronic and electromagnetic tracking systems. Med Phys, 2002. 29(5):
p. 905-12.
Hummel, J.B., et al., Design and application of an assessment protocol for
electromagnetic tracking systems. Med Phys, 2005. 32(7): p. 2371-9.
Meskers, C.G., et al., Calibration of the "Flock of Birds" electromagnetic tracking device
and its application in shoulder motion studies. J Biomech, 1999. 32(6): p. 629-33.
Santanam, L., et al., Fiducial-based translational localization accuracy of electromagnetic
tracking system and on-board kilovoltage imaging system. Int J Radiat Oncol Biol Phys,
2008. 70(3): p. 892-9.
Willoughby, T.R., et al., Target localization and real-time tracking using the Calypso 4D
localization system in patients with localized prostate cancer. Int J Radiat Oncol Biol
Phys, 2006. 65(2): p. 528-34.
Evaluation of Collision Space
Calypso System during Commissioning
Calibration to Isocenter
End to End test
1
2
3
4
5
Scan of Phantom
Treatment Plan of Phantom
Localization of Phantom
Orthogonal Films of Central Target
Analysis
Localization on
Treatment Planning
System: IR Example1
Tome RSNA 2002
Setup of at Treatment Machine using
Optical Guidance: Example 1
Tome RSNA 2002
Resulting Film: Measure of Total
Accuracy of System
Predicted error:
Results:
Z-Pixel Size = 1.25mm
Z: 0.49 mm to T
X-Pixel Size = 0.703 mm
X: 0.35 mm to A
Y-Pixel Size = 0.703 mm
Y: 0.50 mm High
Predicted Error = 1.59mm
Overall error = 0.789mm
Tome RSNA 2002
Example 2: Phantom for Calypso system
(Treatment plan of Implanted target)
Example 2: Phantom for Calypso system
Meeks AAPM 2000
Meeks, AAPM 2000
Test of Localization: Introduce offsets and
measure localization system offset
Phantom
Validation
Digitizer
Beacon® Phantom
3X 1D
Stages
Tracking Accuracy
Measurements
Daily QA
Test
Safety
Method
Collision interlocks
Localization
accuracy
Installation
Test
Accuracy
Pass
Phantom at isocenter
Method
Accuracy
Collision space
Safety
Linac interference with
localization system
Localization system interference
with radiation delivery system
Range of Localization
Move table while localizing to
maximum range
Range of Tracking
Move table while tracking to
maximum range
Tracking Rage
Per manufacturer
specification
Monthly (in addition to Daily): Proposed
Test
Method
Safety
Machine interface: Gating
termination, table autotranslation,
Laser localization
system QA
Following Linac QA TG reports
Isocenter QA
Following Linac QA TG reports
Localization accuracy
System end-to-end test (with CT
scan, treatment plan and
orthogonal portal films)
Tracking accuracy over
clinical range: at
clinical rate of
motion
Motion table
Data transfer
Test patient transferred from
planning system to
localization system
Accuracy in tracking up
to 10cm from
isocenter
Shift phantom from isocenter
Accuracy
Machine spec.
Data transmitted
correctly
Annually (in addition to Monthly)
Test
Safety
Method
Accuracy
Electrical System:
Test/reset buttons &
breakers are functional
Pass
Emergency off buttons are
functional
Pass
System mounting brackets
(all cameras are secure)
Pass
Drift in measured
isocenter over time
of use
Alignment vs. time
Reproducibility
Repeat system alignment at
least 10 times to localize
a fixed phantom
System latency and
tracking timing
Accurate motion table
References
Gierga, D.P., et al., Comparison of target registration errors for
multiple image-guided techniques in accelerated partial breast
irradiation. Int J Radiat Oncol Biol Phys, 2008. 70(4): p. 123946.
Serban, M., et al., A deformable phantom for 4D radiotherapy
verification: design and image registration evaluation. Med
Phys, 2008. 35(3): p. 1094-102
Kutcher, G.J., et al., Comprehensive QA for radiation oncology:
report of AAPM Radiation Therapy Committee Task Group 40.
Med Phys, 1994. 21(4): p. 581-618