Image Overlay Guidance for
Needle
Insertion in CT Scanner
Gabor Fichtinger*, Member, IEEE, Anton Deguet, Ken Masamune, Emese
Balogh, Gregory S. Fischer, Member, IEEE,
Herve Mathieu, Russell H. Taylor, Fellow, IEEE, S. James Zinreich, and
Laura M. Fayad
指導老師:張財榮 教授
報告者:吳昱慧
Date:2010/05/04
1
Outline
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Introduction and Background
System concept
CT image overlay device
System integration
– Workflow
– Calibration
• Experiments and Results
• Discussion
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Introduction and Background
• Numerous studies have demonstrated the
potential efficacy of computed tomography
(CT)-guided
• This frequently results in faulty needle
placement attempts, especially in the case of a
deep lesion adjacent to vital structures
3
• The recent appearance of real-time CT
fluoroscopy has brought significant
improvement to needle insertion procedures
• Presently no technological in a simple,
accurate, and inexpensive manner, without
imparting additional radiation
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System concept
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• Acquire a CT slice, flip it horizontally, adjust
its magnification, and then render it on the
display
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• The system creates the impression as if the CT
image was floating inside the body in the
correct pose and magnification
• Needle placement procedures, after the entry
point is selected, three degrees-of-freedom
(dof) motion of the needle needs to be
controlled
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• Physician uses the overlay image to control the
in-plane insertion angle (first dof)
• In the axial plane marked by the gantry’s inner
laser light (second dof)
• The insertion depth (third dof)
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• 2-D image overlay are numerous in
comparison to other virtual reality or display
augmentation methods reviewed earlier
• 2-D image overlay provides optically stable
image it requires only a simple alignment that
does not need to be repeated for each patient
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• The main added benefit of the image overlay is
making preinsertion CT images available for
intraprocedural guidance
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CT image overlay device
• Built two basic prototypes of the CT image
overlay device for preclinical evaluation on
phantoms and human cadavers
• Verified that the overlay device did not
interfere with the laser lights of the scanner
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First prototype of the image overlay system, the
reflection image is in the inner axial laser plane
of the scanner.
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System integration
• Workflow
• A single CT slice is acquired with the fiducials
in place and transferred in DICOM format to
the planning and control software implemented
on a stand-alone computer
• The CT window/level parameters can be
interactively adjusted
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• The computer marks the target and entry
points
• Especially in applications when the target
anatomy is prone to motion due to respiration
or mechanical force
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• Calibration
• Fabricated a calibration phantom containing a
base board and a perpendicular fiducial board
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• CT image and display image pixel size
• Then the scale factors in x and y directions are
calculated
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• The in-plane scaling between the CT and
display image vectors
• If the pixel size is identical in x and y
directions in both the CT and display, then the
scale factors are equal
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• Calculate the required translation p to align the
selected point
• Translate all CT image points
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• The center of rotation is the point selected
previously for translation
• Rotate all CT points by the calculated amount
about the chosen center of rotation
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Experiments and Results
• Head phantom
• Implanted a honeydew melon with multiple
1.5-mmdiameter metal pellets serving as
targets
• Body phantoms
• The overlay device, mounted in the inner laser
plane of the scanner
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• Cadaver experiments
• Spinal nerve blocks and facet joint injections
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• Shoulder and hip arthrographies
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• Pilot Needle Insertion for Musculoskeletal
Biopsy
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Discussion
• This does not cause time delay, because the
physician needs time to enter the scanner room
anyway
• Needle placement experiments with both
phantoms and cadavers were clinically
successful and confirmed in post-insertion CT
imaging
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