Design and control of a novel
hydraulically/pneumatically actuated robotic
system for MRI-guided neurosurgery
Design and control of a novel
hydraulically/pneumatically actuated robotic
system for MRI-guided neurosurgery
12 3
Cyrus Raoufi, Andrew A. Goldenberg Walter Kucharczyk
12
Department of Applied Technology, California State University, Humboldt. Department of Mechanical and Industrial Engineering, University of
3
Toronto, Toronto, Canada. Department of Medical Imaging, University of Toronto, Toronto, Canada. Correspondence should be addressed to
Cyrus Raoufi ([e-mail]), Andrew A. Goldenberg ([e-mail]), and Walter Kucharczyk ([e-mail]).
&
MR-compatibility of materials and devices. Conven-
ABSTRACT tional robotic systems are not suitable for use inside
the MRI scanner because they contain ferromagnetic
In this paper the design of a novel modular materials and electrical circuits. These components
hydraulic/pneumatic actuated tele-robotic sys-cause spatial distortions and impart noise to the MR
tem and a new infrastructure for MRI-guided images, while conversely the magnetic field of the
intervention for closed-bore MRI-guided neuro-MRI system interferes with the electrical circuits.
surgery are presented. Candidate neurosurgical The strong magnetic field dictates that only non-
procedures enabled by this system would ferromagnetic materials can be used for the mechani-
include thermal ablation, radiofrequency abla-cal parts.
tion, deep brain stimulators, and targeted drug The major shortcoming in the use of conventional
delivery. The major focus is the application of the MRI systems for neurosurgery is their reliance on pre-
designed MR-compatible robotic system to MRI-operative MR images. As surgery progresses and ana-
guided brain biopsy. Navigation and operating tomic tissue are removed or distorted, the intracranial
modules were designed to undertake the align-anatomic positional relationship of the brain and sur-
ment and advancement of the surgical needle rounding structures change. This is commonly
respectively. The mechanical design and con-referred to as “brain shift”. Intra-operative changes
trol paradigm are reported. due to tumor resection, brain swelling, and cerebrospinal
fluid (CSF) leakage further increase brain shift [1, 2,
3]. As these processes are unavoidable in most
neurosurgical procedures, they decrease the accuracy
in all surgery that is based on preoperative MR
1. INTRODUCTIONimages [3]. These intra-operative changes make it dif-
The common requirement for most neurosurgical pro-ficult or impossible to accurately determine the true
cedures is to manipulate a surgical tool relative to an intra-operative anatomic position of the anatomic tar-
anatomic target. This includes aligning, orienting, get based on the preoperative images. Accurate local-
and advancing the tool to a specific anatomic target in ization during surgery thus requires the acquisition
the brain. The advantages of robotic-based neurosurgical of intra-operative images. In recent years, advances
procedures are well recognized in the clinical and in computer technology, robotics, and a significant
technical community due to both the locating accu-increase in the accuracy of imaging have helped the
racy and the tele-surgery potential of the robotic sys-clinicians in planning and executing surgical proce-
tems. A neurosurgical procedure is a highly interactive dures in MRI environments. The advantages of surgi-
process and the goal of neurosurgical robotic system is cal robotics are well known in clinical environments
to provide the neurosurgeon with a reliable tool that due to their precisions, accuracy, repeatability, and
augments his or her ability during the operation. Any capability for tele-surgery [4].
surgical robotic system has to meet specific design In the area of MRI-guided tele-surgery, there are
considerations for its intended use such as safety, currently several systems under development. Tajima
capability of being sterilized, fault-tolerancy, accu-et al. [5] designed and built a prototype of an MRI-
racy, stability, and dexterity. MRI-guided applica-compatible manipulator for treatment and diagnosis
tions impose additional demands such as remote con-of heart diseases. Larson et al. [6] developed a
trol, reduced size, lightweight structure, and ability to device to perform minimally invasive interventions
operate in the MRI bore. Primarily, there is the issue of in the breast with real time MRI guidance for the
Keywords: MR-compatible robot; Tele-surgery;
Tele-robotics; Medical robot
J. Biomedical Science and Engineering, 2008, 1, 68-74Scientific
Research
Publishing
JBiSE
Published Online May 2008 in SciRes. http://www.srpublishing.org/journal/jbise
SciRes Copyright © 2008

early detection and treatment of breast cancer. Engi-Nakamura et al. [17] developed and manufactured
neering Services Inc. (Ontario, Canada) has also the 6 DOF manipulator using non ferromagnetic mate-
developed an MR-compatibletele-robotic system for rials (aluminum) and actuated by ultrasonic motors.
prostate surgery [7]. Krieger et al. [8] designed and The goal of our research project is to design, fabri-
developed a novel remotely actuated manipulator cate, and test a hydraulic/pneumatic actuated MR-
(APT-MRI) to access prostate tissue under MRI guid-compatibletele-robotic system for MRI-guided neu-
ance. Fischer et al [9] designed a robotic assistant sys-rosurgery, in particular, the brain biopsy. The
tem using pneumatic components aimed to be used mechanical design and related infrastructure are
for prostate needle placement in a closed-bore MRI reported.
scanner. Kim et al [10] designed and developed a new
master-slave MR-compatible surgical manipulator 2. ROBOT DESIGN
for minimally invasive liver surgery. Chinzei et al. 2.1. MR-compatible robotic system infra-
[11] designed and developed a novel MR-compatible structure
manipulator used to position and direct an axi-MRI-guided tele-robotic system requires surgical
symmetric tool such as laser pointer or a biopsy cath-planning, MR-image acquisition, human-machine
eter. Moser et al. [12] designed and developed a one interface, navigation, and sensing. To address those
DOF MR-compatible master-slave robotics system components required for MRI-guided intervention,
and a haptic interface using hydraulic transmission. an infrastructure is needed regardless of the type of
Koseki et al. [13] designed and developed an endo-surgical operation. A schematic diagram of the pro-
scope manipulator for trans-nasal neurosurgery capa-posed infrastructure is illustrated in . The
ble of being used inside the gantry of vertical field entire system consists of three main subsystems as
open MRI. Flueckiger et al. [14] proposed a haptic follows: (i) operating unit; (ii) power/control unit;
interface compatible with MR scanner for neurosci-and (iii) surgeon-machine interface unit. The operat-
ence studies. Miyata et al. [15] designed and devel-ing and surgeon-machine interface units are commu-
oped an MR-compatible forceps manipulator using a nicating through MR images and related information
new cam mechanism for the multi-function using an image processing device. The image pro-
micromanipulator system for neurosurgery proce-cessing device is used to provide information
dures. Engineering Services Inc. has also developed required by both the surgeon-machine interface unit
an MR-compatibletele-robotic system using water and power/control unit. The operating unit and
hydraulic and pneumatic actuators for neurosurgery power/control unit are communicating through
[7]. The Calgary Health Region and University of Cal-power transmission and sensory information systems.
gary are developing the world's first image guided Also, the surgeon-machine interface and power/control
TM
neurosurgical robot (NeuroArm) in collaboration units are communicating through operation inputs
with MD Robotics for micro-neurosurgery. The robot created by operator input device (master).
is under design and construction stage now [16]. As shown, all three units communicate through
Figure 1
Figure 1. A schematic of the entire system.
SciRes JBiSE Copyright © 2008
69
C. Raoufi et al./J. Biomedical Science and Engineering 1 (2008) 68-74
Operating Unit
Power/Control Unit
Surgeon-Machine Interface Unit
Hydraulic and Pneumatic
Valves
Operation Input
Image Information
Sensor Information
Control Singnal
Power Transmission
Surgeon
MRI monitoring
display
Image processing
device
Screen control
user interface
Operator input device
(Master)
Motion
controller
Hydralic/Pneumatic
Valves
Patient
Surgical
Table Closed MRI Scanner
Head holder
Slave Manipulator

image information, sensory information, control sig-the head holder is considered as a major component
nals, and power transmission. As illustrated, the visu-in the proposed infrastructure for application of the
alization of the surgical tool and the target as well as tele-robotic system in MR-guided neurosurgery pro-
surgical planning based on intra-operative MR cedures.
images are completed on a display monitor in front of
the surgeon in the surgeon-machine interface unit. 2.3. Manipulator power/control unit
One should note that the proposed infrastructure is The manipulator power/control unit is located in an
based on a fundamental principle which is both the adjacent control room at a proper distance away from
surgeon and power/control unit share the control of the MR scanner due to electrical/electronic devices
the tele-robotic system such that the surgeon will use and circuits as well as non-MR-compatiblematerials
his/her judgment and expertise to control the entire used in its structure. The major function of the manip-
procedure. In other words, it is almost impossible to ulator power/control unit is to provide required
eliminate the surgeon from the control system and power to the slave manipulator. The power/control
have the entire tele-robotic system performed the unit consists of two major sub-units: (i) hydraulic
required task autonomously. power units, hydraulic valves, and pneumatic valves;
and (ii) motion controller devices such as computer
2.2. Operating unitand electrical/electronic components and circuits.
Operating unit comprises the slave manipulator, head The surgeon could manipulate the slave manipulator
holder, surgical table, and MRI scanner located in inside the MR scanner through a master manipulator
MR operating room. The patient's head and the slave located in the surgeon-machine interface unit. The
manipulator are fixed to the surgical table in order to motion controller in the power/control unit is also
avoid any relative displacement during the surgical communicating with the master manipulator in the
operation. The patient's head needs to be secured and surgeon-machine interface unit to provide appropri-
fixed in all surgical operations to avoid unexpected ate control signals to hydraulic and pneumatic valves.
motions caused by disorderly reaction of the patient's The motion controller also receives the sensory data
body. feedback from the slave manipulator. In addition, the
Due to the presence of strong magnetic field and motion controller is also provided with the MR
switching gradients both the head holder and the images data originated from the image processing
slave manipulator are required to be constructed from device as shown in .
MR-compatible materials and devices. The slave
manipulator must perform the required tasks in a con-2.4. Surgeon-machine interface unit
fined space between the patient and the bore of the The major function of the surgeon-machine interface
MR scanner. Therefore, the slave manipulator is unit is to provide an interface between the entire tele-
needed to be designed in a very compact size. In addi-robotic system and the surgeon as the end user. The
tion, the slave manipulator required to be registered goal of using tele-robotic system for MR-guided neu-
with respect to the MR scanner such that the position rosurgery is not to replace the surgeon with the robot,
and orientation of the surgical tool with respect to the but to provide him/her with advanced tools for
target could be determined based on data obtained remote execution of neurosurgical procedures. The
from the MR images. One should note that the unit is located in the adjacent control room to avoid
patient's head must be secured during the operation magnetic interference due to use of electrical devices
as the desired position and orientation of the surgical and non-MRI-compatible materials used in its struc-
tool with respect to the target will be obtained while ture. A master and a screen control user interface are
the surgical device is outside the patient's skull. Thus, the major subsystems of this unit. The images of the
Figure 1
Figure 2. 3D model of the slave manipulator.Figure 3. 3D model of the navigation module.
SciRes JBiSE Copyright © 2008
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C. Raoufi et al./J. Biomedical Science and Engineering 1 (2008) 68-74
Navigation Module
Biopsy Module
Connecting Arm
Locking Mechanism
Surgical Arm
Base Plate
Hydraulic Cylinder
Moving Plate

slave and surrounding environment are projected on
the screen to allow visualization of the target and sur-
gical tools movements. The surgeon would manipu-
late the position and orientation of the surgical
devices via the master controller. Surgeons strongly
rely on the visual MR images as they are only reliable
source of information during the operation. The
screen control user interface is the unit that provides
the visualization of the tissue and surgical tool while
the operation progresses. There are several important It consists of a base plate and a moving plate
challenging issues that one must consider in design-interconnected through 6 links. Each link consists of
ing the screen control user interface including [18]: (i) a hydraulic linear actuator, a spherical joint, and a uni-
integration of navigation and display with robot sys-versal joint.
tems; (ii) updating the MR images in real time; (iii)
providing the surgeon with means of controlling the 2.7. Biopsy module and locking mechanism
information displayed; and (iv) finding ways to com-A 3D model of the biopsy module is presented in
municate useful information without overwhelming It is basically a three-plate mechanism including: (i)
the surgeon by pointless details. The master manipu-a lower fixed plate, (ii) anupper fixed plate, and (iii)
lator is the unit with which surgeons could communi-a moving plate. Both lower and upper fixed plates are
cate their control commands. Any commonly used attached to the base plate by two sets of screws. Two
interfaces for human-machine interactions such as guide pins are used to support the moving plate. The
mice, joystick, touch screens, push buttons, and foot moving plate is moved up and down using a pneu-
switches could be used. matic rodless cylinder. The moving plate is attached
to the slide of the pneumatic cylinder. A 3D model of
2.5. Mechanical design for the slave manipu-the locking system is shown in The locking
lator system consists of a connecting arm and locking mecha-
A 3D model of the slave manipulator is shown in nism. As shown, the locking mechanism is attached to the
The surgical needle is held and advanced by base plate of the parallel mechanism through the con-
the biopsy module. The biopsy module is attached to necting arm. All mechanical parts are constructed
the navigation module.from MR-compatible materials.
The navigation module is a six degrees of freedom
parallel mechanism consisting of a base and a plat-2.8. Surgical arm
form interconnected through 6 legs (or struts). Six lin-The surgical arm supports both the navigation and
ear hydraulic actuators are used to provide required biopsy modules during the operation. The surgical
linear displacement for each leg. A locking mecha-arm has to be easily maneuvered by the clinician to be
nism is used to guide the needle as well as lock the located at the entry point on the patient's skull. The
robot at desired orientation. It is fixed to the base of design of the surgical arm is shown in . It
the parallel mechanism through a connecting arm by consists of two links and three joints as follows: (i) a
screws. All three units (the navigation module, spherical joint 1; (ii) a revolute joint 2; and (iii) a
biopsy module, and the locking mechanism) are held spherical joint 2. The Spherical-Revolute-Spherical
by a surgical arm. The surgical arm is attached to a (SRS) arm is illustrated in fully deployed configura-
surgical table through a set of screws.tion in order to show its components and correspond-
ing function of each component. As shown, rod 1 con-
2.6. Navigation modulenects the SRS arm to the surgical table and rod 2, at
A 3D model of the navigation module is shown in the other end, connects the navigation module to the
ure 3.
Figure
4.
Figure 2.
Fig-
ure 2.
Figure 5
Fig-
Figure 4. 3D model of the biopsy module.
SciRes JBiSECopyright © 2008
C. Raoufi et al./J. Biomedical Science and Engineering 1 (2008) 68-74 71
Figure 5. A schematic diagram of the surgical arm.
Rod 2 to connect
SRS arm to the
navigation module
Spherical
Joint 2
Revolute
Joint
Link 2
Link 1
Spherical
Joint 1
Rod 1 to connect
SRS to the surgical
table
Pneumatic Motor
Rodless Pneumatic Cylinder
Slide
Upper Fixed
Plate
Moving Plate
Guide Pines
Base Plate
Lower Fixed
Plate
Biopsy Needle

operative images as visual feedback. When the nee-
dle reaches the target, it is rotated by 180 degrees in
order to cut the tissue specimen (tumor). Then the nee-
dle is pulled out completing the operation.
(6)Final stage. The MRI table is moved out the MRI
bore. The slave manipulator and head holder are
detached from the table and patient's skull respec-
tively.
3.2. Robot control architecture
As mentioned, the surgeon adjusts the orientation of
the surgical tool (yaw and pitch angles) based on
visual MR images through the master. The inverse
kinematics of the navigation module is used to obtain
the desired length of each strut related to the desired
position and orientation of the needle biopsy.
The hydraulic/pneumatic circuit of the system and
overall control system are shown in and
respectively. Six MR-compatible hydraulic cyl-
inders are equipped with six fiber optic encoders to
SRS arm.feedback the actual length of each strut. Using
inverse kinematic of the navigation module, the
desired length of each strut of the navigation module
3. ROBOT CONTROLis determined. A PID controller provides a control sig-
3.1. Needle alignment nal that drives a hydraulic proportional valve in each
An entry point, a surgical tool and a target are servo control loop. The hydraulic valve controls the
depicted in . Required motions to align and length of the strut by regulating the flow from/to each
advance the surgical tool with respect to the target hydraulic actuator. In addition, a pneumatic valve
are also shown. The surgical tool is rotated about the (V7) is used to control the tip position of the biopsy
burr-hole by Yaw and Pitch angles. This point is also needle. The semi-rotary pneumatic motor is also actu-
called the pivot point. The conventional surgical tool ated by an on/off pneumatic valve (V8).
placement at an entry point includes the following A block diagram of the control algorithm used in
three tasks: (i) move the needle tip to the entry point the controller is shown in . The inputs are
using 3 DOFs; (ii) orient the needle by pivoting six feedback displacement signals from the slave side
around the entry point using 2DOF (Yaw and Pitch (LA1, LA2, LA3, LA4, LA5, and LA6), two signals
angles); and (iii) insert the needle into the body using form master side including desired Yaw and Pitch
1 DOF (translation along a straight trajectory). Using angels, and desired length of each strut (LD1, LD2,
the proposed tele-robotic system shown in , LD3, LD4, LD5, and LD6). The outputs are control
the brain biopsy procedure would be carried out as fol-signals (S1, S2, S3, S4, S5, and S6) to control the pro-
lows: portional valves.
(1)Preoperative imaging stage. The patient is A PC-based supervisory controller is designed to
placed inside the MRI scanner and preoperative control entire system as illustrated in . The
images are obtained. trajectory of each joint is calculated based on the
(2)Surgical planning stage. Based on the pre-inverse kinematics in a PC-based supervisory con-
operative images, an entry point is determined and troller and fed to each joint controller RS485 Bus. As
the incision is made by a surgeon. shown in , six optical encoders are used to
(3)Pre-alignment stage. The slave manipulator is feedback the position signals to six microprocessors.
attached to the surgical table, and the navigation mod-Each actuator has individual microprocessor to con-
ule and biopsy needle are manually located at the trol its proportional valve.
entry point. Although this stage doesn't require high
accuracy in positioning, the slave has to be locked 4. CONCLUSION AND FUTURE WORK
such that the surgical tool is positioned at the entry We have designed an MR-compatible tele-robotic sys-
point. Accurate alignment with respect to target will tem that can be used for orientation and advancement
be done in the next stage; of a biopsy needle on the brain biopsy procedure. The
(4)Real time navigation stage. The patient is moved robot has been designed such that it will perform
into the bore of MRI scanner. The navigation module desired tasks inside MR scanner GE Signa 1.5T. To
is maneuvered remotely in order to align the surgical date, design and analysis of the entire system have
tool with the desired direction based on intra-been completed. Material selection and the controller
operative images. architecture and its component have been finalized.
(5)Intra-operative operation stage. The operation A physical prototype of the slave manipulator is in
is carried out by advancing the needle using intra-the process of being constructed. Current and future
Figure 7Fig-
ure 8
Figure 6
Figure 9
Figure 1
Figure 10
Figure 10
SciRes JBiSE Copyright © 2008
72
C. Raoufi et al./J. Biomedical Science and Engineering 1 (2008) 68-74
Figure 6. The target, entry point, and the needle.
Burr Hole
(Pivot point)Surgical ToolAxial
Pitch/Yaw
Roll
Target

Figure 9. A schematic of overall control architecture.
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C. Raoufi et al./J. Biomedical Science and Engineering 1 (2008) 68-74 73
Figure 8. A schematic of overall control architecture.
Figure 7. A schematic of hydraulic/pneumatic circuit.
Copmuter or/and Panel
Surgeon
Input
Master
PC Based Controller
FID CONTROLLER
Inverse
Kinematic
Rodless Cylinder
Semi-rotary pneumatic
motor V8
V7
V6
V5
V4
V3
V2
V1
V1
V2
V3
V4
V5
V6
V7
V8
A6
A5
A4
A3
A2
A1
Hydranlic Unit
Compressed
Air
Air Pre-preparation
Unit
Low magnetic fieldInside MR scanner
Semi-rotary Motor
Rodless Cylinder
Desired Lenghts:
LD1
LD2
LD3
LD4
LD5
LD6
Control Singnals:
S1
S2
S3
S4
S5
S6
Trajectory Planing
Inverse kinematic Master
Desired trajectory:
Yaw Angel
Pitch Angel
Actual Lenghts
La1 La4
La2 La5
La3 La6
PID Controller
Optical Encoders
Proportional ValvesHydraulic Actuators

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ACKNOWLEDGEMENTS 2001 Australian Conference on Robotics and Automation
This work was partially supported by Natural Sciences and Engi-2001, Sydney.
neering Research Council of Canada (NSERC), grant held by Pro-[12]R. Moser, R. Gassert, E. Burdet, L. Sache, H. Woodtli, J. Erni,
fessor Andrew A. Goldenberg and Ontario Research and Develop-W. Maeder & H. Bleuler. An MR-compatibleRobot Technol-
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C. Raoufi et al./J. Biomedical Science and Engineering 1 (2008) 68-74
Figure 10. Supervisory control configuration.
Supervisory Controller PC
Rs485 Bus
Joint Control:
Microprocessor(6)
Proportional
Valve(V6)
Optical
Sensor(S6)
Joint 6
Joint Control:
Microprocessor(2)
Proportional
Valve(V2)
Optical
Sensor(S2)
Joint 2
Joint 1
Joint Control:
Microprocessor(1)
Proportional
Valve(V1)
Optical
Sensor(S1)