Computed Tomography (CT) guidance - research.cs.queensu.ca€¦ · Title: CISST ERC: Key Facts...

Copyright © Gabor Fichtinger, 10/15/2017Laboratory for Percutaneous Surgery – The Perk Lab

Computed Tomography (CT)

guidance


Concept of Computed Tomography (CT)

Planar fan beam


CT scanners


CT gantry inside


Examples to CT imaging


• 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


Navigation between CT slices

thk = slice thickness (cm or mm)

012 k -- slice index


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)


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


Tilted CT gantry

z

yNo longer a Cartesian

coordinate system


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.


To navigate the tool to a certain target point along a predefined

trajectory according to a plan made relative to CT images

Navigation challenge


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


Mark the plane of interest with fiducial strip

Scanner laser


Calculate needle angle () and depth (d)

A(i1,j1)

B(i2,j2)

x

x

d


Pick the entry point based on fiducial

NeoRad.com


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


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


Handheld needle guide

Bubble level + protractorFichtinger, et al.


CT-mounted laser overlay

Fichtinger, et al.


SimpliCT device by NeoRad

NeoRad.com


CT image overlay

Fichtinger, et al.


The Picker/Marconi/Philips/Immersion

“Pinpoint” device

Immersion


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

z-stage-RCM-Paky-CT.mpg


Tracked navigation

StealthStation® by

Medtronic


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


Coordinate frames and transformations


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


We localize markers and compute Fhm in

tracker coordinates

Fhm


We localize markers and compute Fhm in CT

coordinates

Fhm


Track the surgical tool & graphically

superimpose on CT


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

http://www.youtube.com/watch?v=SbpN4vFgQSY

http://www.youtube.com/watch?v=idpGakc0pUA

http://www.youtube.com/watch?v=1fQxSJqEU9g

http://www.youtube.com/watch?v=kmbWtR36GYc


BUT: we need to know Ptm and vtm … but how?


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

Computed Tomography (CT) guidance - research.cs.queensu.ca€¦ · Title: CISST ERC: Key Facts...

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