[robotics-worldwide] [jobs] PhD proposal: Perception and rendering of tissues stiffness in minimally invasive medical and surgical procedures, in Strasbourg/Paris

bbayle bernard.bayle at unistra.fr
Wed May 6 02:03:51 PDT 2015

Perception and rendering of tissues stiffness in minimally invasive medical
and surgical procedures

Minimally invasive techniques have considerably modified surgery during the
last three decades.  Laparoscopic surgery, in particular, has been
developing in many specialties, such as urology, digestive surgery, or
gynecologic surgery. If they present numerous advantages for the patient
(less scars, infection risks and a shorter recovery period), these surgical
techniques have an influence on the surgeon perception. The natural
perception of tissues properties resulting from palpation is no longer
possible. The interactions are not direct and therefore less natural.  This
induces difficulties to perform the gestures and limits the use of
laparoscopic access to rather simple interventions.

In endoscopic surgery, the introduction of rigid tools in the body comes
with an artifact, the  Fulcrum (or lever) effect. Because of the rotation of
the tools about a fixed point, the motions inside and outside the body are
in opposite directions, which requires a particular training. Also, the
respective magnitude of the movements of the operator’s hand and of the
surgical tool varies, depending on the tool insertion depth . Finally, the
lever effect also modifies the forces, which leads to a distorted perception
of stiffness. If li denotes the length of the tool within the body, and lo
the length of the tool outside the body, it can be easily shown that the
stiffness perceived at the tool is the real stiffness multiplied by
(li/lo)^2.  This naturally provides misleading feedback, and this is even
amplified when the distal motions are observed on a screen, with and
endoscope, whose amplification is fixed and does not depend on the lever. 

To assist medical interventions, robotic means are proposed in the
literature, where two main approaches exist (cf. Figure 1):
•	Telemanipulation, which assumes that a slave arm manipulates the
instrument, tracking the motions imposed by the surgeon on a master arm.
This approach has proved successful because of its clinical development, but
force feedback is not allowed by present commercial systems, used in the
operating room. As a result, the available systems cannot solve the problems
of stiffness perception;
•	Collaborative manipulation (or comanipulation), a paradigm for which the
surgeon and the robot jointly manipulate the tool, which allows the robot to
apply forces to guide the surgeon. The interest of this approach lies in its
simplicity and modularity. However, the choice of the robot impedance in
order to take the lever effect into account remains an open problem. 

Figure 1: two approaches for the assistance to surgical gestures in
laparoscopic surgery 
(left: telemanipulation; right: comanipulation)

In this thesis, we will compare two possible approaches: 
•	an approach for which the tool is manipulated through a variable stiffness
device, allowing to correct the Fulcrum effect (comanipulation) ;
•	an approach for which the manipulated tool has a constant stiffness, but
is teleoperated in a way that the force feedback may restore the actual
stiffness to the operator, removing the distortion due to the Fulcrum

The study will explore the mechatronic design of variable stiffness systems,
the control aspects, but also the sensorimotor behavior of the operator. It
will consist, in particular to understand, if the operator can move the
distal point of the instrument, in the same manner as it is performed in
conventional open surgery. A possibility will be to use the analysis of
gestures kinematics and stiffness perception. The influence of training
(comparison between expert surgeons and beginers) will be a particular
problem of interest.

This work is collaboration between  ICUBE laboratory, in Strasbourg, and
ISIR laboratory in Paris, within the frame of the Computer Assisted Medical
Interventions excellence laboratory (CAMI LABEX). It takes place in the
continuation of research led in Strasbourg on telemanipulation and variable
stiffness robots, and in Paris on collaborative manipulation. The thesis
will mostly take place in Strasbourg, but a significant stay in Paris will
be considered.

The candidate will ideally have a multidisciplinary profile with skills in
Control/Robotics but also in mechatronic design. Less polyvalent profiles,
with a strong skill will however be considered. A real interest for
experimentation is required. 

[1] Wagner, C. R., Stylopoulos, N., and Howe, R. D. The role of force
feedback in surgery : Analysis of blunt dissection. In Symposium on Haptic
Interfaces for Virtual Environment and Teleoperator Systems,  2002.

[2] B. Bayle, L. Barbé, Tele-manipulation, Medical Robotics, Jocelyne
Troccaz (Eds.), Chapitre 8,  Wiley, 2012.

[3] Morel G., Szewczyk J., Vitrani M.-A., chapitre Comanipulation, Medical
Robotics, Jocelyne Troccaz (Eds.), Chapitre 9, Wiley, 2012.

[4] Esteveny L., Vers un actionnement sûr pour la radiologie
interventionnelle robotisée, thèse de lUniversité de Strasbourg, 2014.

[5] I. Nisky, F. Huang, A. Milstein, C.M. Pugh, F. Mussa-Ivaldi, A. Karniel.
Perception of stiffness in laparoscopy - the fulcrum effect. Stud Health
Technol Inform. 2012; 173:313-9.

[6] A. Mattar , S. Nasirk , M. Darainy, D. Ostry, Sensory change following
motor learning,   in Progress in Brain Research, A. M. Green, C. E. Chapman,
J. F. Kalaska and F. Lepore (Eds.), Vol. 191 ISSN: 0079-6123.

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