Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Computed Tomography (CT)
guidance
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Concept of Computed Tomography (CT)
Planar fan beam
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
CT scanners
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
CT gantry inside
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Examples to CT imaging
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
• Widely available
• Reasonable cost
• Broad insurance coverage
• Excellent hard tissue image
• Reasonable soft tissue image
• 2D by nature
• Limited angles
• X-ray dose
• Access to patient
Siemens
Pros and cons of CT
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Navigation between CT slices
thk = slice thickness (cm or mm)
012 k -- slice index
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Navigation in a CT Slice
NX number of pixels (typically 512)
FOVX size of the body captured (in cm)
dx = FOVX / NX (pixel size, in cm)
NY
num
ber
of
pix
els
(ty
pic
ally
512)
FO
VY
siz
e o
f th
e b
ody c
aptu
red (
in c
m)
dy =
FO
VY
/ N
Y (
pix
el siz
e,
in c
m)
i – pixel (column index)j –
pix
el (r
ow
in
dex)
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Conversion between pixel and metric
coordinates in CT imaging
Simple scaling:
P(x,y,z) = P(i*dx, j*dy, k*thk)
Where:
dx = FOVX / NX
dy = FOVY / NY
&
FOVX, FOVY, NX, NY, thk are
usually printed on the CT image
header
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Tilted CT gantry
z
yNo longer a Cartesian
coordinate system
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
CT gantry with parallel laser planes
Scan plane laser Gantry laser
The two laser planes are parallel, orthogonal to the table, and the
distance between the planes is known.
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
To navigate the tool to a certain target point along a predefined
trajectory according to a plan made relative to CT images
Navigation challenge
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Example: spinal needle placement
Targeted areas in facet joint injection (left), nerve block (middle), and epidural
space injection (right). All figures show the lumbar spine. Facet joint injections and
nerve blocks are also frequently performed on the thoracic and cervical spine.
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk LabSunday, 15 October 2017
Needle insertion as a 5-DOF problem
3-DOF
Cartesian
2-DOF pivoting 1-DOF or
2 -DOF insertion
Safe but feasible Must be very
accurate
Assumes no bending
and accurate depth
Decoupled motion
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Mark the plane of interest with fiducial strip
Scanner laser
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Calculate needle angle () and depth (d)
A(i1,j1)
B(i2,j2)
x
x
d
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Pick the entry point based on fiducial
NeoRad.com
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
The challenge
• Transfer entry, angle and depth onto the patient
• Control all 5 DOF simultaneously during insertion
A(i1,j1)
B(i2,j2)
x
x d
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Workflow for CT-guided manual injection
1. Put patient in the scanner
2. Palpate vertebra
3. Take thin volume scan
4. Select slice of interest
5. Affix fiducial strip
6. Take single slice
7. Pick target and entry
8. Determine angle and depth
9. Identify entry on skin
10. Touch needle to entry point
11. Maintain insertion angle
12. Keep needle in laser plane
13. Judge current insertion depth
14. Insert contrast (if need to)
15. Push patient back to scan plane
16. Take confirmation CT
17. Pull out patient
18. Inject therapeutic agent
A(i1,j1)
B(i2,j2)
x
x
d
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Handheld needle guide
Bubble level + protractorFichtinger, et al.
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
CT-mounted laser overlay
Fichtinger, et al.
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk LabSunday, 15 October 2017
SimpliCT device by NeoRad
NeoRad.com
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk LabSunday, 15 October 2017
CT image overlay
Fichtinger, et al.
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk LabSunday, 15 October 2017
The Picker/Marconi/Philips/Immersion
“Pinpoint” device
Immersion
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Robot registered to CT from a single
image using stereotactic frame on the
end-effector
Credits:
Registration: Fichtinger, Masamune
Robot: Stoianovici, Patriciu
Clinical: Kavoussi, Solomon
(Johns Hopkins University)
Robotic assistance
MOVIE
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Tracked navigation
StealthStation® by
Medtronic
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Coordinate frames and transformations
Computer screen Operating room
Fhm
Fhm
Fct
Ftm
Ftr
Fcthm
Ftrtm
Fhmtr
Fhmtm
Ftt-tm
Ftt-ct
tr= tracker
tm=Tool marker
hm=head marker
ct= CT scanner
tm=Tool marker
hm=head marker
Ptm
vtm
Pct vct
Phm=Fhmtr*Ftrtm Ptm
vhm=Fhmtr*Ftrtm vtm
Pct=Fcthm*Phm
vct=Fcthm*vhm
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Coordinate frames and transformations
Computer screen Operating room
Fhm
Fhm
Fct
Ftm
Ftr
Fcthm
Ftrtm
Fhmtr
Fhmtm
Ftt-tm
tr= tracker
tm=Tool marker
hm=head marker
ct= CT scanner
tm=Tool marker
hm=head marker
Ptm
vtm
Pct vct
Phm=Fhmtr*Ftrtm Ptm
vhm=Fhmtr*Ftrtm vtm
Pct=Fcthm*Fhmtr*Ftrtm Ptm
vct=Fcthm* Fhmtr*Ftrtm vtm
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
We localize markers and compute Fhm in
tracker coordinates
Fhm
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
We localize markers and compute Fhm in CT
coordinates
Fhm
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Track the surgical tool & graphically
superimpose on CT
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
Example: Tracked CT-guided sinus surgery
3D Image Guided Endoscopic Sinus Surgery
http://www.youtube.com/watch?v=SbpN4vFgQSY
Computer assisted sinus surgery or image guided sinus surgery
http://www.youtube.com/watch?v=idpGakc0pUA
CT-Guided Computer assisted or image guided sinus surgery
http://www.youtube.com/watch?v=1fQxSJqEU9g
CT-Guided Dental Implant - Computer assisted or image guided
sinus surgery
http://www.youtube.com/watch?v=kmbWtR36GYc
Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab
BUT: we need to know Ptm and vtm … but how?
Computer screen Operating room
Fhm
Fhm
Fct
Ftm
Ftr
Fcthm
Ftrtm
Fhmtr
Fhmtm
Ftt-tm
tr= tracker
tm=Tool marker
hm=head marker
ct= CT scanner
tm=Tool marker
hm=head marker
Ptm
vtm
Pct vct
Phm=Fhmtr*Ftrtm Ptm
vhm=Fhmtr*Ftrtm vtm
Pct=Fcthm*Fhmtr*Ftrtm Ptm
vct=Fcthm* Fhmtr*Ftrtm vtm