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loutclankedAI and Robotics

Nov 13, 2013 (3 years and 11 months ago)

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Introduction to
Robotics in
Medicine


Part 1: Problems in Navigation

Achim Schweikard


Introduction


Types of Medical Robots:



1. Master
-
Slave
-
Systems for Telesurgery


2. Robots for Navigation


3. Robotic Imaging

Master
-
Slave Robotic System

Master
-
Slave Robotic System


Purpose: Microsurgery


Surgeon motion can be downscaled


E.g. Surgeon moves hand of master robot
by 1 cm, slave robot moves by only 1 mm.

Robots for Navigation

Robots for Navigation


Purpose: Robot guides the instrument


Example: Cutting plane is calculated by
robot. Surgeon can move the robot in the
plane

Application for Navigation:

find the precise angle for drilling

Epiphyseolysis

Stabilization

Osteotomy

Femoral Repositioning

Implant navigation

CT image data

tumor

Problem: Navigate Placement of
Implant

Further Application

Navigate placement of stabilizing screw


Avoid Perforation

[1] PM Riley et. al. (1990)

Hazards of Internal Fixation in the treatment of slipped femoral epiphysis, JBJS 72
-
A: 1505

[2] RT Loder et. al. Slipped Femoral Epiphysis, JBJS 82
-
A, 1170
-
1188

Principle



Infrared system can compute exact spatial
position of active probes



Capture position of X
-
ray camera, target
and instrument via infrared tracking
system

Fluoroscopic navigation

System Overview


Fluoroscopic Navigation



X
-
ray Camera (C
-
arm) must be movable


Instrument must be movable


Target (Bone) may move


Indications

sphere
target
line (3D)
target
line (2D)
camera
surface
intersection
point
projection lines
projection plane (image)
Navigation with x
-
rays: Screen

Navigation in Bone Surgery


Maxillofacial Surgery


Orthopedic Surgery


Trauma Surgery



Passive, semi
-
active and active navigation

Problem for Navigation with x
-
ray:
Magnetic Distortion


Earth‘s magnetic field causes bending of
straight lines in the images. Thus images
are not accurate. Image must be corrected

Problem for Navigation with x
-
ray:
Magnetic Distortion

Magnetic Distortion

Distortion parameters vary with the position of the x
-
ray camera

Three Types of Navigation

Passive (Surgeon moves the instrument, guided by

images on computer)

Semi
-
active (Robot holds the instrument,



e.g. restricted to one plane, surgeon drives the

instrument in forward direction)

Active (Robot holds and moves the instrument alone,

example: Cyberknife radiosurgery.

Surgeon cannot be in room due to radiation)

Semi
-
Active Navigation

Problem in this context


Registration: find appropriate position for
two images relative to one another, such
that given anatomical structures in both
images match



Registration


Example: surface of a bone has been
extracted from a CT (tomography) data
set.



Second image set shows same bone in
MR
-
tomography.


Goal: Find matching position („CT
-
MR
-
fusion“)

Registration

CT: blue, MR: gray

CT
-
Segmentation

(bone contour outlined)

Same bone in MR
-
tomography

bone surface (cortical bone) appears black in MR

Goal of Registration

Overlay CT and MR, such that bone contours match


Many other similar registration problems

occur in navigation systems

33

Comparison

CT

MR

34

After Registration

Problem for registration



Distortion Correction for MR required


MR image is often distorted



36

Correction of MR
-
Distortion

Before correction

after correction

Further Problem in Navigation:
Image Segmentation

-
Segmentation is often
helpful for better
registration

-
But: Registration can also
help segmentation

38

Examples


Segmentation in tissue surface and cavities

MRI

Segmentation

Distortions

Femur bone distortion in MR

Femur Bone Segmentation

The End…