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Proceedings of the Xth Meeting of the World Society for Stereotactic and
Functional Neurosurgery, Maebashi, Japan, October 1989
Stereotact Funct Neurosurg 1990:54+55:468-470
Configuration of a Robot Dedicated to Stereotactic
D. Glausera, P. Flurya, Ph. Durr\ H. Funakuboa,
C. W. Burckhardta, J. Favreh, P. Schnyderc, H. Fankhauserb
3 Department of Microengineering, Swiss Federal Institute of Technology;
Departments of b Neurosurgery and c Radiology, Centre Hospitalier Universitaire
Vaudois, Lausanne, Switzerland
Key Words. Robot • Stereotactic techniques
Abstract. The design of a robot for functional stereotactic surgery which is under
construction in our laboratory is described. The main features include operation inside
the computed tomographic (CT) scanner, the possibility of intraoperative CT scanning
and complete handling of the stereotactic probes by the robot.
' This study was supported by a grant of the Swiss National Science Foundation.
© I990S. Karger AG. Basel
101\ - 6 125/90/0554-0468 S 2.75/0
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Stereotactic surgery represents the medical field which most obvi­
ously could benefit from robotization. Indeed, stereotactic interven­
tions involve repetitive and monotonous steps ideally suited for a ro­
bot. The specific surgical work represents only a minimal part, as sug­
gested by the fact that functional stereotactic procedures are performed
by neurologists as well as by neurosurgeons.
Several teams are working on stereotactic robots which are able to
move an arm and position a probe guide in order to assist the surgeon
during the operation [1-3]. The computer calculates the coordinates
and commands the movements of the robot which positions the probe
guide along the stereotactic trajectory.
We are elaborating the next step which includes handling of the
probes by the robot.
Stereotactic Robot
Different stereotactic interventions have been classified in order to increase the
complexity as far as the instrument manipulation is concerned. Functional stereotaxy is
most simple, followed by hematoma evacuation, stereotactic biopsy, brachytherapy and
tumor resection. A list of specifications has therefore been elaborated for a stereotactic
thalamotomy robot. This includes the following features. (1) The whole intervention is
performed inside the computed tomographic (CT) scan. (2) It is possible to perform CT
scanning at different levels during the intervention, without the necessity to move the in­
struments or the robot. (3) The robot is compatible with a nondedicated CT scanner,
which requires minimal preparation and occupation time and no significant technical
modification of the scanner itself. (4) The entire intervention is performed by the robot,
including skin and bone penetration and change of instruments, but excluding handling
of the hair, skin disinfection, administration of local anesthesia and skin suture. (5) In
the course of thalamotomy, 5 different instruments can be manipulated by the robot
without physical human intervention. These include a skin perforator and external guide
tube, a drill, a dura perforator and 2 stereotactic instruments.
Up to now we have designed the various parts of the robot. Prototypes of different
elements are now tested in our laboratory and in the collaborating hospital. Numerous
problems have come to light and solutions have to be adapted continuously. The main
features of the robot include the following.
Since intraoperative CT scanning will be performed, the head of the patient and the
base of the robot are linked together in a completely rigid manner. The head and robot
have to move together with the CT table. Our solution includes a second CT platform
with its own floorstand which is brought into the CT room, positioned behind the gantry,
and which can be linked to the CT table. This platform carries the stereotactic frame, the
referential system, the head of the patient and the robot. It is moved passively by the CT
table. The robot has 5 distinct units which are the arm, the wrist, the skin-poking unit, the
probe positioner and the probe-stocking unit. The arm positions the system at a specific
point in space. The wrist function is given the proper orientation according to the stereo­
tactic trajectory and to allow an axial movement to penetrate the skin. At this point the
arm, the wrist and the skin-poking unit are locked. The function of the probe positioner
is to provide all axial movements along the stereotactic trajectory, including drilling of
the bone and introduction of the electrode. Some probes have their own intrinsic move­
ments such as rotation for the drill or the side-outlet electrode. Each probe will be a sepa­
rate unit, but all will have the same connecting system to fit the probe-stocking unit. For
safety reasons all probe movements are manually reversible in case of a power failure.
Initially, the robot will provide capability to handle the following 5 instruments:
The external guide tube with a cutting extremity containing a removable inner tube will
open the skin and act as a guide during the operation. The external guide tube will be
slowly rotating and advancing and cut a 3-mm disk of skin. A firm contact with the skull
will be established. The skin will then be evacuated by retraction of the inner tube. The
external guide tube will remain in place. Next, a drill will be advanced through the guide
tube. Through torque control, the drill will recognize contact with the skull, penetration
into the diploe and penetration of the inner table. Further advance of the drill is automat­
ically stopped at this point. A sharp pointer is advanced next in order to ensure proper
perforation of the dura and pia mater. The following 2 instruments will be a straight elec­
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Material and Methods
trode and a side-outlet electrode, the rotation and coaxial movement of which will be
controlled by the robotic wrist probe positioner.
The whole system needs extensive computerization for target selection, calculation,
display of the trajectory, as well as control of the robot. We aim at maximal indepen­
dence from the computer of the CT scan and the constraints imposed by its manufactur­
ers. For these reasons we have connected a personal computer which immediately takes
over the noncompressed image data from the CT. Image display and sagittal reconstruc­
tions for target selection will be performed on our own computer. These will be corre­
lated with a simple but accurate volumetric stereotactic atlas written in Turbo-Pascal.
Commands for the robots will be generated from this same computer and transmit­
ted to the robot control unit.
Robotization of stereotactic interventions not only allows entry
into an exciting new technological field with unforeseen applications,
but it may also significantly improve present stereotactic interventions
by adding speed, accuracy and security. Nevertheless, numerous obsta­
cles have been encountered. The most significant difficulties not di­
rectly related to robotic technology include: (1) insufficient mechanical
precision, stability and weight-bearing capacity of the CT table; (2) lim­
ited space in and behind the CT scan; (3) limitations due to hardware
and software protection by the CT manufacturer; (4) nonexistence of
adapted high-quality electrodes, and (5) sterility conditions. These
problems have not been previously addressed in the literature. We have
elaborated potential solutions for all steps, and we are now in the
course of manufacturing, testing and adapting prototypes.
Kwoh YS: Special stereotactic technique: Robotic methods applied to stereotactic
surgery: in Heiibrun MP (ed): Stereotactic Neurosurgery. Baltimore, Williams &
Wilkins, 1988, pp 219-226.
Young RF: Application of robotics to stereotactic neurosurgery. Neurology 1987;
Benabid AL, Cinquin P, Lavalle S, Le Bas JF, Demongeot J, de Rougemont J:
Computer-driven robot for stereotactic surgery connected to CT scan and magnetic
resonance imaging: Technological design and preliminary results. Appl Neurophy­
siol 1987;50:153-154.
D. Glauser, Departement de Microtechnique, EPFL,
CH-I015 Lausanne (Switzerland)
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