Editorial Original Articles Review Article Case Report Clinical Topics

60 Pages·2006·1.08 MB·English

Vol.49, No.11&12 November/December 2006
Editorial
New Surgical Robotics for Clinical Use in Neurosurgery
Makoto Hashizume................................................................................................................................................ 333
Original Articles
Development of Surgical Manipulator System “HUMAN” for Clinical Neurosurgery
Koji Nishizawa, Masakatsu G Fujie, Kazuhiro Hongo, Takeyoshi Dohi, Hiroshi Iseki............................. 335
An Analysis of Ambulance-transported Cases of Attempted Suicide in 3 Prefectures
(Akita, Aomori, and Iwate) in the Northern Tohoku Area in Japan
Chikara Yonekawa, Hajime Nakae, Kimitaka Tajimi, Yutaka Motohashi, Yasushi Asari,
Shigeatsu Endo, Sergio A Perez Barrero........................................................................................................... 345
Gender Differences in Symptom Experience at End-of-Life among Elderly
Patients Dying at Home with Advanced Cancer in Japan
Yoshihisa Hirakawa, Yuichiro Masuda, Masafumi Kuzuya, Akihisa Iguchi,
Kazumasa Uemura ................................................................................................................................................ 351
Change of Plasma High Sensitive
—C reactive protein levels in climbers
Shintaro Suzuki, Yuji Kiuchi, Tetsuya Nemoto, Kenta Kobayashi, Hidekazu Ota..................................... 358
The Effectiveness of a New Law to Reduce Alcohol-impaired Driving in Japan
Takashi Nagata, David Hemenway, Melissa J Perry........................................................................................ 365
Review Article
Child Abuse in Japan: Current problems and future perspectives
Makiko Okuyama.................................................................................................................................................. 370
Case Report
A Case of Juvenile Temporal Arteritis with Eosinophilia Accompanied with
Eosinophilic Vasculitis of Both Lower Legs and Swelling of the Bilateral
Inguinal Lymph Nodes
Taro Mikami, Seiko Kou, Hiroshi Sakamoto, Kuniaki Bando, Eriko Takebayashi,
Hitoshi Komatsu, Youichi Iemoto...................................................................................................................... 375
Clinical Topics in Japan
Symptoms and Treatment of Andropause
Shigeo Horie........................................................................................................................................................... 382
Table of Contents......................................................................................................................................... 385
Acknowledgement to Reviewers....................................................................................................... 391
Editorial
New Surgical Robotics for Clinical Use
in Neurosurgery
Makoto Hashizume*1
Minimally invasive surgery (MIS) has become so the system to microsurgery such as neurosurgery
explosively popularized throughout the world where there are so many critical conditions to be
because there is a significant difference in the resolved. The target area is surrounded by the so
postoperative quality of life of the patients with important normal tissue that the access to the
MIS from that with open surgery. The patients deeper targeting area is limited. The paper by
can enjoy earlier recovery to normal life or nor- Nishizawa et al. in this issue of the journal is
mal activity after MIS than after conventional considered significant, as they have developed
open surgery. Although there are clear benefits, new surgical robotics with the concept of MIS via
MIS has also some disadvantages for the sur- a single insertion part and the prior-confirmation
geons. Long instruments placed through fixed based safety control. It required several technical
entry points creating a fulcrum effect, with the developments to enable the performance of MIS
surgical field viewed on a 2-D screen and with the via a single hole. They made neurosurgery in
camera under an assistant’s control, create an one-opening craniotomy under fine and accurate
unnatural environment where the surgeon loses control to avoid damage to the surrounding
orientation, the eye-hand-target axis, and visual important normal tissues.
depth perception. All these obstacles reduce the The issue of interference between mechanical
surgeon’s normal dexterity and limit his ability to elements was solved by developing a hollow
deal with difficult situations. flexible torque tube with one end segment of the
Computer-aided surgery, known as Robotic hollow pipe. This mechanism allows the torque
surgery, is proposed to overcome some of the and thrust for rotation and translation move-
drawbacks of traditional MIS.1 This technology ments successfully transmitted to the joint at
includes master-slave telemanipulator systems. the tip of the manipulator, resulting in the pro-
The goals of these surgical systems are to enhance duction of fine and high performance with an
manipulation capabilities and to increase the per- accuracy of less than 10(cid:1)m. There is no need for
formance precision. It provides secure precise concern over collision among the arms holding
procedures without any limitation in whichever the manipulators and medical staff. There is a
direction the operator desires. The da Vinci is the serious problem in Japan that some parties have
most popular surgical robotic system among the discontinued the development of therapeutic
commercially available types. More than 430 sets tools. This paper is thus highly evaluated as the
of the da Vinci are already installed all over the authors have confirmed the basic function of the
world at present. More than 300 sets are installed new robotics in clinical settings.
in the United States and more than 50 sets are in The authors evaluated the feasibility of robotics
Europe. Robotic surgery provides you with a 3 for clinical use, especially focused on safety con-
dimensional view as well as 7 degrees of freedom trol. Actual movement of the manipulator takes
of the instruments with an articulate at the tip. It places only after prior calculation of the position
is easier for you to perform complicated proce- that would result from the input manipulate. They
dures such as ligature or suturing with a needle in
a confined space. That is the reason why more
*1 Department of Disaster and Emergency Medicine, Graduate
than 40 percent of all prostatectomies have been
School of Medical Sciences, Kyushu University, Fukuoka
performed with the surgical robotic system in the Correspondence to: Makoto Hashizume MD, PhD, FACS, Department
United States. of Disaster and Emergency Medicine, Graduate School of Medical
Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku,
However, the size of the robotics is so large at
Fukuoka-shi, Fukuoka 812-8582, Japan. Tel: [phone],
this moment that it has been impossible to apply Fax: [phone], E-mail: [email protected]
JMAJ, November/December 2006—Vol. 49, No. 11•12 333
call the safety control system “prior-confirmation the function rather than the structure of the
based safety control.” It prevents any movement organ or disease.2 In this concept, termed bio-
of the manipulator beyond the predetermined surgery by Randall Wolf, MD, the purpose will
range in the field of neurosurgery. These fine and be to change the biological processes of the body
accurate control systems as well as safety control though direct modification of cellular, molecular,
make it possible to perform MIS via one-opening metabolic, and perhaps even genetic processes.
craniotomy in neurosurgery, which was impos- The new robotic system developed by Nishizawa
sible in conventional methods. This provides et al. will lead us to the second step towards
the possibility of expanding MIS to other fields attaining the goal.
of microsurgery. Although the working area is
limited to that within 1cm3 in the present robotic References
system, the utility and possibility would be fur-
1. Hashizume M, Tsugawa, K. Robotic surgery and cancer: the
ther expanded with the development of technol- present state, problems and future vision. Jpn J Clin Oncol.
ogy on molecular image or genetic information. 2004;34(5):227–237.
2. Satava RM. Robotic surgery: from past to future—a personal
The goal of future surgery will be to change journey. Surg Clin N Am. 2003;83:1491–1500.
334 JMAJ, November/December 2006—Vol. 49, No. 11•12
Original Article
Development of Surgical Manipulator System
“HUMAN” for Clinical Neurosurgery
JMAJ 49(11•12): 335–344, 2006
Koji Nishizawa,*1,2 Masakatsu G Fujie,*3 Kazuhiro Hongo,*4 Takeyoshi Dohi,*5 Hiroshi Iseki*6
Abstract
Surgery using manipulator systems for medical treatment has recently attracted considerable attention as
a method for realizing certain minimally invasive surgeries. In the field of navel surgery, some manipulator
systems for medical treatments are used in Europe and the United States. However, it is inappropriate to apply
these systems to neurosurgery because the size of the manipulators is too large, and only one of them can be
used in one insertion part. To solve this problem, we developed the manipulator system “HUMAN”, which
has an insertion part with a diameter of 10mm and contains one endoscope and three manipulators. In this paper,
we propose the concept for realizing minimally invasive surgery, and discuss the mechanism and control of
our developed system based on this concept. A clinical application using this system was successfully performed
in August 2002, and was successful. Since the manipulator is so small that operation is possible from one
small incision, this system is effective in realizing certain minimally invasive neurosurgeries.
Key words Surgical support, Master-slave manipulator system, Neurosurgery, Clinical application
difficulty in the manipulation of surgical tools
Introduction is a major drawback of this procedure as com-
pared with open surgery. As an alternative way to
The development of minimally invasive surgery, safely perform minimally invasive surgery, much
involving as little damage to the body as pos- attention has recently been directed at the use of
sible, is strongly desired as a means to alleviate surgical manipulators incorporating robot tech-
the physical and psychological suffering of pa- nology. There are several surgical manipulators
tients and to accelerate postoperative recovery. currently applied to clinical use mainly in West-
In a form of such surgery known as laparoscopic ern countries, such as the da Vinci® and ZEUS®
surgery, a surgical operation is performed using systems, which have been fairly well appraised
a laparoscope, and surgical tools such as slender by clinicians for good maneuverability.2–5
forceps are inserted through small incisions. This Realization of minimally invasive surgery has
type of surgery has been popularized rapidly also been pursued in the field of neurosurgery.
since the first successful laparoscopic cholecys- For example, procedures such as thermal treat-
tectomy was performed by Muhe et al. in 1985.1 ment and biopsy using neuro-endoscopes have
Although laparoscopic surgery has the ad- entered practical use.6 However, the applicability
vantage of low invasiveness, the high degree of of this method is limited to simple movements,
*1 Graduate School of Medicine, Tokyo Women’s Medical University, Tokyo; *2 Mechanical Engineering Research Laboratory, Hitachi, Ltd.,
Hitachinaka; *3 School of Science and Engineering, Waseda University, Tokyo; *4 Department of Neurosurgery, Shinshu University School of
Medicine, Matsumoto; *5 Institute of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, Tokyo; *6 Institute
of Advanced Biomedical Engineering & Science, Tokyo Women’s Medical University, Tokyo
Correspondence to: Hiroshi Iseki MD, Koji Nishizawa, Faculty of Advanced Techno-Surgery, Institute of Advanced Biomedical Engineering &
Science, Graduate School of Medicine, Tokyo Women’s Medical University, 8-1 Kawada-cho Shinjuku-ku, Tokyo 162-8666, Japan.
Tel: [phone], Fax: [phone], E-mail: [email protected], [email protected]
A part of this study was presented at the 41st Annual Conference of the Japanese Society for Medical and Biological Engineering held in
Sapporo on June 3-5, 2003.
JMAJ, November/December 2006—Vol. 49, No. 11•12 335
Nishizawa K, Fujie MG, Hongo K, et al.
and the reality is that enucleation of tumors and where avoidance of pressure on tissues is desired.
other operations involving delicate and compli- To realize minimally invasive surgery in the
cated manipulation are normally performed by field of neurosurgery, it is thus required to create
means of extensive craniotomy and microsurgery a system that allows the insertion of an endo-
under a surgical microscope.2 The realization of scope and multiple surgical tools through one
minimally invasive surgery remains a problem small cranial opening and supports the delicate
to be solved. and accurate manipulation of these tools. With
As compared with abdominal operations in this consideration in mind, we developed the
general, neurosurgery requires considerations re- manipulator system “HUMAN”.7 In August 2002,
garding the following characteristics: 1) import- we succeeded in the world’s first clinical applica-
ant normal tissues are located densely around tion of HUMAN in the field of neurosurgery,8
the lesion; 2) tissues are prone to damage and and so far have used this system in the treat-
susceptible to pressure; 3) the field of operation ment of four patients.
is limited to a small area; 4) there are strict limi- Based on the concept of minimally invasive
tations on the site of the craniotomy providing surgery in the field of neurosurgery, this paper
an approach to the lesion site; and 5) manipula- describes the mechanism of the HUMAN system
tion must be controlled finely and accurately to developed to realize the use in clinical settings.
avoid damage to normal tissues. It also reports the results of our study confirm-
To realize minimally invasive surgery that can ing the practical effectiveness of this system in
provide an alternative to conventional crani- clinical use.
otomy, we must be able to perform a dexterous
surgical operation in which the surgeon can ma- Minimally Invasive Surgery Using
nipulate multiple slender surgical tools inserted the HUMAN System
through one small cranial opening in such a way
that the lesion may be treated accurately without The purpose of the HUMAN system is to per-
causing pressure or damage to the surrounding form a surgical operation using an endoscope
normal tissues. Such an extremely delicate sur- and three manipulators inserted through a cra-
gical operation can not be performed by human nial opening with a diameter of 10mm. The
hands. target of treatment is a tumor with a volume of
Existing surgical manipulator systems such about 1cm3. While larger tumors need extensive
as da Vinci® and ZEUS® are not suitable for use craniotomy, cases of small tumors in this size
in neurosurgery, because of the size and config- range are greatly helped by the use of minimally
uration of their surgical tools and other devices invasive surgery, which is also effective in the
involved. In these systems, each manipulator improvement of the patient’s quality of life
consists of a surgical tool at one end and a bulky (QOL).
drive mechanism at the other end, and this struc- This manipulator is capable of performing
ture results in physical interference when mul- more finely controlled motions than the human
tiple manipulators are used in close proximity. hand and, thus, realizes more delicate surgical
To avoid such interference, devices are set up treatment. After further development for prac-
so that the manipulators and the endoscope are tical use, this system may be combined with
inserted into the patient’s body through separate conventional surgery as an advanced surgical
incisions. In addition, the surgical tools used in instrument supporting delicate operations in
the da Vinci® system have a diameter as large as about 30% of cases with malignant brain tumors.
11mm.3 Due to these factors, it is impossible to It will also enable us to treat small tumors in
insert the set of manipulators needed for treat- locations that have been inoperable on with
ment through one small cranial opening. If we conventional methods as well as to perform pre-
try to avoid interference by inserting manipula- cise removal of residual tumors located adjacent
tors through more than one cranial opening, it to functional areas.
would be difficult to secure the approach route
for each surgical tool, and a wide field of opera- Mechanism of the HUMAN System
tion would be required. This method, therefore,
is not appropriate in the field of neurosurgery, Fig. 1 shows an external view of the HUMAN
336 JMAJ, November/December 2006—Vol. 49, No. 11•12
DEVELOPMENT OF SURGICAL MANIPULATOR SYSTEM “HUMAN” FOR CLINICAL NEUROSURGERY
Manipulators Three-dimensional endoscope
Monitor
Operation
input devices
Holding device
Cylindrical insertion part Operation console
Fig. 1 HUMAN manipulator system
Cylindrical insertion part
(10mm in diameter)

Endoscope
(4mm in diameter)

Manipulator(cid:4)3 (cid:3)
(3.0mm in diameter)

b
(cid:2)
Surgical tool(cid:4)3
(1mm in diameter)

a
(cid:1)
Fig. 2 Magnified image of cylindrical insertion part
system developed by us, and Fig. 2 shows the consists of a bundle composed of an endoscope
details of the cylindrical insertion part. While (4mm in diameter) and three manipulators
observing the endoscopic image at the center of (3mm in diameter). At the tip of each mani-
Fig. 1, the surgeon uses the operation input de- pulator is a detachable surgical tool (1mm in
vices to the right of the figure to perform a surgi- diameter). The spaces in the bundle of the mani-
cal operation via the action of the manipulators pulators and endoscope contain five irrigation
shown on the left of the figure and in Fig. 2. tubes that can be used for dripping and suction.
The operation input device detects the force Each manipulator has three degrees of freedom,
applied by the surgeon on the operation lever corresponding to (cid:1) (bending), (cid:2) (rotation), and
with a resolving power of 7.8mN. It controls (cid:3) (translation) indicated in Fig. 2. Each surgical
the position of the operation lever in response tool has a two degrees of freedom, correspond-
to the applied force and prevents movement ing to a (opening/closing) and b (rotation rela-
beyond the range of permitted motion. tive to the joint) in Fig. 2.
The insertion part (with a diameter of 10mm) Table 1 summarizes the specification values
JMAJ, November/December 2006—Vol. 49, No. 11•12 337
Nishizawa K, Fujie MG, Hongo K, et al.
Table 1 Working area and minimum distance
Driving wire
DOF (cid:1) (cid:2) (cid:3) 1.0 mm
Working area 1/2(cid:1)rad 2(cid:1) rad 50mm 2.8 mm 2.4 mm
Minimum distance 8(cid:5)m 2(cid:5)m 5(cid:5)m Top part
(designed value) ((cid:1)(cid:6)0rad) ((cid:1)(cid:6)(cid:1)/2rad) Rotation axis
2.0 mm
Base part
Fig. 3 Hollow micro joint
Drive wire Pulse motor ((cid:1))
Hollow Pulse motor ((cid:2)) Hollow
micro joint Drive guide
Hollow wire tube
rigid pipe
(cid:2)
(cid:1)
(cid:3)
Ball screw Adapter
Spring
Pulse motor ((cid:3))
Fig. 4 Drive mechanism of manipulator and micro joint
for the range of movement (working area) and in the tip of the manipulator. To realize the mini-
the smallest step of tool-tip movement (mini- ature moving mechanism, a pair of studs on the
mum distance) in each direction of the three top (distal) part has been fitted into correspond-
degrees of freedom. Here, the minimum distance ing holes in the base part to form a rotation axis.
refers to the tool-tip displacement resulting The base part and the top part are designed as
from the one-pulse action of the pulse motor hollow tubes with the inside diameters of 2mm
used in the manipulator drive mechanism. Be- and 1mm, respectively, so that a surgical tool
cause the minimum distances regarding cocking with a diameter of 1mm can be housed within
and rotation depend on the cocking angle at the joint.
the beginning of movement, the Table gives the Fig. 4 shows a schematic illustration of the
values corresponding to the positions where the manipulator drive mechanism. The end of a drive
minimum distance would be the largest. wire, connected to the top part of the micro-
The manipulator drive mechanism and the joint, is connected to the motor controlling the
endoscope are attached to the holding device angle of the joint in the (cid:1) direction (Fig. 2). This
via an adapter. The holding device inserts the part of the drive mechanism is called the bending
insertion part into the field of operation in re- unit. Rotation is realized by revolving the hollow
sponse to the surgeon’s manipulation. To ensure rigid pipe together with the micro-joint and the
safety, insertion is performed with the entire bending unit in the (cid:2) direction (Fig. 2). Trans-
manipulator assembly contained within the in- lation is realized by the ball screw producing
sertion part. Manipulators extrude from the in- fine linear motion of the hollow rigid pipe, the
sertion part when used in treatment. bending unit, and the rotation mechanism as a
Fig. 3 shows the structure of the micro-joint whole in the Z direction (Fig. 2). This structure
338 JMAJ, November/December 2006—Vol. 49, No. 11•12
DEVELOPMENT OF SURGICAL MANIPULATOR SYSTEM “HUMAN” FOR CLINICAL NEUROSURGERY
HUMAN Manipulator 1Hollow rigid part Dofr imvea nmipeuclhaatonrism
Hollow
Hollow flexible
micro joint Drive mechanism
torque tube
of surgical tool
(3 mm in diameter)
Hollow rigid pipe Rigid three-dimensional
(3 mm in diameter) endoscope
Lense of endoscope Hollow guide
(4 mm in diameter) tube
Cylindrical
insertion part
Surgical (10 mm in diameter)
tool
Adapter
HUMAN Manipulator 2 Drive mechanisDomfr isovufe r mgmiacenacilph tuaolnoailtsomr
Fig. 5 Structure of thin bundle system
using the nesting of drive mechanisms for differ- mechanism of the HUMAN manipulator in
ent motions ensures freedom from interference Fig. 5) exerts the torque and thrust for rotation
between different motions, thereby improving and translation movements, the action is effi-
the stability and reliability of movement. ciently transmitted to the joint at the tip of the
manipulator.
Thin-bundle System Combining
Multiple Manipulators Mechanism for Changing Surgical
Tools
To be able to operate multiple manipulators as
a bundle in the inserted part, interference be- A surgical manipulator must have a mechanism
tween manipulator drive mechanisms, as well as for changing surgical tools without replacing the
that between them and the camera unit of the manipulator itself so that the development of
endoscope, needs to be avoided. A mechanism surgical tools may be facilitated and a variety of
allowing smooth rotation and translation in the surgical tools can be used during an operation.
bundle of multiple manipulators is also needed. To create this mechanism for changing sur-
In this system, one end segment of the hollow gical tools, we designed the HUMAN system is
pipe shown in Fig. 4 is made of a hollow flexible designed to have a hollow structure as shown
torque tube, which is curved and fitted in an in Fig. 4. We developed a surgical-tool unit that
adapter so that the drive mechanisms of the enables various surgical tools to be attached to
multiple manipulators are kept in place without and removed from the tip joint by means of
causing mutual interference. Fig. 5 illustrates insertion and withdrawal through the bore. We
the system with an endoscope and two HUMAN also developed various tools that can be attached
manipulators installed. This structure solves the and removed in this way; including those with
problem of interference between mechanical driving mechanisms, such as tweezers, biopsy
elements. While avoiding interference, the flexi- forceps, scissors, and bipolar forceps,9 and those
ble torque tube transmits the torque and thrust without driving mechanisms, such as monopolar
for rotation and translation movements along tools, S-shaped hooks, spatulas, and needles.
the curved path. When the drive mechanism The surgical-tool unit consists of a power-
(shown in Fig. 4; located in an area of the drive transmission part, with an outside diameter of
JMAJ, November/December 2006—Vol. 49, No. 11•12 339
Nishizawa K, Fujie MG, Hongo K, et al.
Gripper Shape memory alloy spring
Transmition part of tension
b
Forceps
Drive mechanism
Fig. 6 Surgical-tool unit
Positioning Drive mechanism
blade of surgical tool
Tool adapter
Surgical tool
Entrance of
hollow guide
tube
Manipulator Drive mechanism
adapter of manipulator
Fig. 7 Usage of exchangeable adapter module
1mm, which extends from the drive mechanism of treatment operation.
and has a pair of forceps at the tip (Fig. 6). The To achieve this rotation capability, the forceps
opening and closing motions of the gripper part must be able to be bent toward in direction and
are controlled by transmission of the power follow the bending of the joint. To this end, the
produced by the drive mechanism via the drive part corresponding to the movable part of the
wire located in the tension-transmission part. micro-joint on a neck of the forceps has been
A torque tube with high torque-transmission designed with a super-elastic shape-memory-
efficiency is used in the tension-transmission alloy spring (Fig. 6). This super-elastic material
part. With this mechanism, the tool inserted in has the advantage of high flexibility combined
the joint can be rotated (motion labeled “b” with the resistance to plastic deformation. Irre-
in Fig. 2 and Fig. 6) by the twisting motion of spective of the direction of the opening and
the power-transmission part applied to the drive closing of the tool relative to the bending direc-
mechanism, and the tool can be inserted and tion of the joint, this structure of forceps en-
withdrawn freely even when the path in the hol- ables the surgical tool unit to follow the bending
low tube is curved as in Fig. 5. The ability to motion of the manipulator without interference.
rotate the surgical tool enables the direction of At the same time, this structure with a shape-
the opening and closing of the tool to be changed memory-alloy spring prevents permanent curling
relative to the direction of joint bending ((cid:1) in of the device in a certain direction, realizing a
Fig. 2), thereby improving the maneuverability durable system suitable for practical use.
340 JMAJ, November/December 2006—Vol. 49, No. 11•12
DEVELOPMENT OF SURGICAL MANIPULATOR SYSTEM “HUMAN” FOR CLINICAL NEUROSURGERY
Tube Blade spring
A Handle A
B
Guiding
pipe
B
A A
Tool adapter
Fig. 8 Tool holder
Fig. 7 illustrates how the surgical unit is in-
stalled. The surgical tool is fixed to the manipu- Safety Control
lator by a newly developed adapter module
consisting of a tool adapter and a manipulator Because conventional systems are targeted at
adapter complementing it. The tool adapter is use in the abdominal cavity, they are designed
fixed to the end of the surgical-tool drive mech- to move the manipulator over a wide area with
anism (Fig. 7). The manipulator adapter is fixed a spatial resolution of several millimeters. In the
to the bending unit (to the extreme right in Fig. position-control systems developed for such
4 and in Fig. 7). At the center of this adapter, applications, the position of the operating lever
there is an entrance leading to the bore of the responding to the surgeon’s maneuver is sam-
manipulator. The surgical tool is inserted from pled at a frequency of 1,000 times per second
here and is led through the hollow path to the and feedback to the manipulator.
joint tip. The tool adapter is then connected to In contrast, because our system is intended
the manipulator adapter using a rotating motion, for neurosurgery, it can perform fine movements
which integrates the tool and manipulator drive at steps smaller than 10(cid:5)m in volumes as small
mechanisms. This connection also integrates the as 1cm3, as shown in Table 1. It detects the input
inserted tool with the micro-joint as shown in force applied by the surgeon at a frequency of
Fig. 2. Similarly to the structure shown in Fig. 4, 250 times per second and with a resolving power
this structure avoids mutual interference be- of 7.8mN. According to the detected amount
tween different motions of the manipulator and of input movement, the position after the exe-
the surgical tool, realizing good stability and reli- cution of movement is calculated and actual
ability of motions during use of the manipulator movement is performed only when the calcu-
with surgical tools attached. lated result falls within the prescribed range
Fig. 8 schematically shows the surgical-tool of allowed movement. This method of control,
holder, which is used for attaching monopolar developed for this system to ensure safety, is
forceps and other dedicated tools with no drive called “prior-confirmation-based safety control”.
mechanism, as well as third-party flexible surgical Compared with frequency of position detection
tools, to the manipulator. Also attached to this of conventional systems, that of our system is
holder is a tool adapter that can be attached lower, but a higher degree of safety is realized,
to the manipulator drive mechanism in place of because safety is confirmed before actual move-
the tool drive mechanism. The surgical tool is ment and the resolving power is finer than that
inserted into the guiding pipe connected to the of conventional systems by a factor of 100. In
bore of the manipulator, and this tool is held this way, our system prevents any movement
by handles. As an example, we experimentally of the manipulator beyond the predetermined
confirmed the feasibility of this holder in using range in the field of neurosurgery, where the
third-party optical fibers for laser knives.10 safety of the surrounding normal tissues is crit-
JMAJ, November/December 2006—Vol. 49, No. 11•12 341