Why IGST
• Trend towards minimally-invasive
procedures
• Minimize Patient trauma but..
• Minimally-invasive procedures restrict
view of operative site.
• Medical images give information that
otherwise cannot be seen
• Allows increase in precision of tracking
and guidance
Image-guided Surgery in the
Brain and Heart
Terry Peters
Robarts Research Institute
University of Western Ontario
London, Canada
Surgery or Therapy?
• Parkinsons’ Disease surgery
– Remove brain cells to suppress positive
feedback of electrical signals in the brain
Surgery is a side-effect of therapy
• Coronary Artery Bypass
– Sew on new vessel to bypass occlusion
• Cardiac Arrhythmia
– Remove few abnormally firing cells.
Surgery or Therapy (cont)
Solution
• Most neurosurgery –
• Enter body through “ports”
• Use active probes / laparoscopic
instruments
• Full view of organ not available
• Use imaging
– Craniotomy
•
Most cardiac surgery
–
–
–
–
Split sternum
Open chest
Stop heart
Cardiac bypass machine
– Pre-operative
– Intra-operative
• Complications are due to access surgery,
NOT therapy.
Page 1
Image-guided Surgery and
Therapy (IGST)
100+ years later:
• First published example McGill 1896
(<6 months after Roentgen discovered
X-rays)
• Removal of bullet from leg of gunshot
victim based on X-ray image
• Quantitative image-guided surgery
began with stereotactic neurosurgery
• Trend towards minimally-invasive procedures
Image-guided surgery/therapy
Image Guided Neurosurgery
• Minimally-invasive procedures complemented
by sophisticated imaging
• Images provide information that otherwise is
unavailable to surgeon
• Allows increased precision for
– Planning procedure
– tracking and guiding instruments during the
procedure
• Use preoperative imaging as an intraoperative
guide
• Brain, Heart, Kidney, Prostate, Breast
– e.g. CT, MRI, MRA, PET and fMRI
• Avoids major trauma through minimallyinvasive approach
• Requires visualization of organs beneath
surface
• Register pre-operative images to patient, or
• Image patient during surgery, or
• Combination of both approaches
• Tracking device provides real world (patient)
coordinates, mouse provides image coordinates
• External land marks on patient/frame are matched
with image landmarks to determine patient
→ image transformation
• Assumes no tissue motion during procedure
Traditional Stereotactic
Neurosurgery
Traditional IGS of Brain:
Stereotactic Neurosurgery
• Frame mounted on
the skull defines a
surgical coordinate
system
• Surgeon uses
medical images to
locate the target
prior to surgery
• A frame mounted on
the skull defines a
surgical coordinate
system
• The surgeon uses
medical images to
locate the target
prior to surgery
Page 2
Stereotactic Surgery
Stereotactic Images
• Positions of Fiducials
define slice geometry
with respect to frame.
• Target coordinates
calculated manually or
via software
• Coordinates of target
set up on stereotactic
frame
Stereotactic Frame
X=110, y=76, z=35
Plates containing fiducial markers
fastened to plates
Stereotactic Planning with
Stereoscopic Multi-modality
Imaging
From Planning to Guidance
• Planning
– Target specific site
– Biopsies, deep-brain lesioning, electrophysiology
– Procedure performed using reference to frame
coordinates
• Guidance
–
–
–
–
Intra-operative Image Guidance
Register patient with images
Track tools interactively during procedure
Real-time update of probe position in 3-D image
(Image in real time during surgery)
Guidance Systems
•
•
•
•
•
Page 3
Need to track tools
Mechanical
Magnetic
Optical
Ultrasonic
Tracking Systems for IGS
Intraoperative tracking
in OR
Optical tracker
M TL
image
LEDs
M WT
HeadClamp
M LP
patient
Tracked Probe
pointer
Fixed Reference
M PW
Probe position measured with
respect to fixed reference
rather than camera
Stereotactic MR Image
Navigation Issues
•
•
•
•
•
Minimally-invasive Surgery
Challenge
Accurate target placement
Accurate target coverage
Avoidance of sensitive tissues
Minimize unnecessary tissue damage
Minimize patient trauma
IGNS Platform
Requirements
•
•
•
•
•
User Friendly
Tracking facilities
2-D and 3-D
Multi-modality
Frame-based and non-frame
procedures
• Open ended
Page 4
Atlases
• Anatomical images don’t show
everything
• Nuclei in deep brain not seen directly
via MRI or CT
• Defined by electrophysiology
• “Text-book” atlases
• Apply to anatomical images for
navigation
Atlases
Electrophysiology Atlas
• Record electrophysiological data in
individual patients (stimuli, responses)
• Note stereotactic coordinates
• Non-linear warp to standard brain
• Accumulate database in standard brain
• Apply database to patient via non-linear
warp
Deep brain atlas as defined by
Schaltenbrand mapped to
(standard brain)
Same atlas as non-linearly
mapped to patient’s brain
Electro-physiology
Database
Foot
Hand
Lips
Page 5
Thalamocapsular Border
Results: Functional Borders
Microelectrode Recording:
Paresthetic
(Microstim)
Kinesthetic
(MER)
Muscle Contraction(Macrostim
Contraction
)
Green - Kinesthetic
( 40 patients)
Red
- Pressure responsive
(22 patients)
Yellow - Tactile
(36 patients)
Orientation
axial
Axial
*
Sagittal image, right hemisphere, A: anterior
Sagittal
Open-craniotomy: Tissue
moves during surgery
Targeting structures in thalamus
• Intra-operative MRI
• Intra-operative ultrasound
• Model effect of intra-operative
procedure on tissue
• Integrate with pre-operative images
• Warp pre-op
intra-op image
Courtesy Dr W Kucharzuck, Toronto
Page 6
Integrate 3-D MRI and
Ultrasound
Interactive 3D warping
Intra-Operative MR/US warp
Minimally-invasive Heart Surgery
raft
bypass
rtery
oronary
CABG
Minimally Invasive Bypass
Surgery
Laparoscopic Techniques
• Endoscope,
laparoscopic
instruments
• Manual operation
• Surgeon tremor
magnified
• “Mirror-image” surgery
• Difficult to perform
delicate surgery with
cumbersome controls
mechanically-linked to
operating tools
• Same benefits as conventional bypass surgery– restores blood flow, oxygen, nutrients to heart.
• Additional advantages
– surgeon works on beating heart through smaller incisions.
• Shorter length of stay:
– discharged after 2 to 3 days, cf 5 - 10 days for
conventional CABG surgery.
• Faster recovery:
– no heart -lung machine and smaller incisions
– reduces complication risk of stroke and renal failure
– resume normal activities in 2 weeks cf 6 - 8 weeks with
conventional surgery.
Page 7
Minimally-invasive Robotically
Assisted Coronary Bypass
(MIRCAB)
Why Robotics?
Non-robotic minimally-invasive
endoscopically-guided surgery
• Overcomes limitations of manuallymanipulated tools and endoscopes
• Controls endoscope and surgical tools
• Voice operated endoscope
• Improved surgeon ergonomics
• Introduces tremor control and gain
• Adaptable for tele-operation
“like signing your name with a metrelong pencil while holding it by the
eraser.”
- Dr. D W Boyd, Cardiac Surgeon, (Ex)
London Canada
MIRCAB
Limitations of MIRCAB
remote surgeon console
patient set-up
• Lack of visual guidance
– setup difficult to plan
– lose context of endoscope
– sub-surface structures (buried vessels /
surgical targets unseen
• Improper thoracic port placement:
– limits access to the target
– robotic arms may collide
– sub-optimal coverage of surgical site
• Limited view of the surgical site due to small FOV of
endoscope
thoracic ports
MIRCAB
Virtual Cardiac Simulation Platform
• Somewhat disappointing results to date
–
–
–
–
New paradigm
Limited access
Excessive OR time
Outcome?
• Image support crucial to robotic-assisted
procedures
– Dr. Michael Mack – “Engineering the future of
Surgery” Symposium, Columbia University NYC
April 2002
Page 8
Image-guidance for Cardiac
Surgery
Endoscope
Robot Arms
Cororary vessels
Image as seen through virtual endoscope
Image Management
• Still major obstacle to efficient use of
images in OR
• ACR-NEMA – DICOM leading the way
towards standardization
• Not all DICOM-3 formats compatible
• DICOM-3 currently still 2-D
• Standard still evolving for multidimensional data
• Correct image dataset in right place at
right time
Obstacles to effective use of IGST
Image Integrity
Actual position
• Diagnosis and therapy impose different
requirements
• MR Image distortion
–
–
–
–
–
Imaged position
Susceptibility
Gradient nonlinearity
Incorrect FOV
Patient motion
RF inhomogeneity
Susceptibility artifact
caused by metal particle
Oil-filled Fiducial markers
moved by Chemical -shift
Segmented image
• CT artifacts
– Beam hardening
– Patient motion
Before RF
intensity correction
Page 9
After RF intensity
correction
Segmented image
User Interface
Usability Issues
• IGS will have greatest impact when it:
–
–
–
–
• IGS systems compatible with all OR
instrumentation?
• Intelligent - recognize instruments?
• Standard user interfaces?
becomes standard operating-room tool
reduces OR time
decreases patient trauma
uses streamlined data management.
• Image/accessibility format
• Image processing
• Industry Standards
• Universal adoption of multi-dimensional
image data structure
– allow images from multiple sources to be
integrated and manipulated effortlessly.
– integrate with hospital information systems
The Challenges
The Challenges (Cont)
• Automatic data management
•
•
•
•
•
User Interface
More effort on human factors issues
Unobtrusive systems
Simple to operate
Minimal additional technical support
– acquisition of images
– merging them with scans from other
sources
– segmenting relevant structures
– automatically / minimum intervention.
• Eliminate keyboard, inconvenient
switching mechanisms in OR
• Simple tailored application solutions for
specific surgical applications
Page 10