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COMPUTER AIDED SURGERY AND MICRO MACHINETakeyoshiDOHI

Graduate School and Faculty of EngineeringThe U niversity of Tokyo

7-3-1 Hongo, Bunkyo-ku, Tokyo 113Japan

Abstract: Computer aided surgery (CAS) is a newsurgical field to realize minimally invasive surgicaltherapy, using various computer technologies whichar e three dim ensional medical images, surgical robotsand so on. Three dimensional medical images ar enew eyes of a surgeon, and surgical robots are newhands of a surgeon. Especially, in ord er to realize theminimally invasive therapy, it is necessary to developnew surgical devices which are needles forpercutaneous puncture, m anipulaters, fine endoscopesand so on using micro machine technology. The mainapplications of th e CAS system are the liver cancertreatment therapy, the laparoscopic surgery, theendoscopic surgery, the stereotaxic neurosurgery, a ndcorneal micro surgery.

1. In t roduct ionA number of the medical instruments have been

developed as diagnostic, therapeutic andadministrative tools. Recently the most advancedmedical devices are equipped with micro-computers, sensors, electric and mechanical elementsbased on knowledge of mechatronics. On the otherhand, it is very difficult to apply these advancedtechnologies to surgical operations. Howeve r, itmeans that there is much left to develop surgicaldevices using various advanced technologies. One ofthe most important problems in the surgic al field is aminimally invasive therapy. To realize minimallyinvasive surgical therapy, it is necessary to usevarious computer technologies which are threedimensional medical images, surgical robots and soon. This new surgical field using comp utertechnology is called Computer aided surgery (CAS).

Sixth International Symposium onMicro Machine and Human Science0-7803-2676-8/95 $4.00 01995 IEEE.

In order to develop the field of computer aidedsurgery, it is necessary to apply three dimensionalmedical images, medical robots, medicalmechatronics, micro machine, laser technology andso on.2. Micro M achine in Minimal ly Invas ive Surgery2.1.Minimal ly Invas ive Surge ry

The main purpose of the minimally invasivesurgery is to realize reduction of patient's physicaldama ge caused by a surgical operation. And thefirst characteristic of this surgery is not to make anybig injury of incision to approach the diseased part.The minimally invasive surgery is expected asfollows;

1)Reduction of patient's physical damage caused2)Shortening of hospital stay and prompt recovery

by a surgical operation.to daily life

Avoidance of a bed-ridden elderly.Lessening or diminishing of rehabilitation.Reduction of medical costs.

3)More safety and accurate procedures compared4)Recovery of patients from incurable disease.5)Surgerie s without transfusions.6)Reduction of physical, mental and labor burden7)Prevention of infection accidents caused by8)App ropriate informed consent for a patient.9)Completeness of medical and specialist

with those in a conventional surgery.

for m edical staffs.hepatitis virus and HIV virus.

education.

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2.2. Micro Machine in Minimally InvasiveSurgeryA micro machine is one of the most expected

technologies for the CAS . Espec ially, thistechnology provides a surgeon with a new hand torealize minimally invasive therapy. Thistechnology is expected to advance micro surgeryunder a microscope, treatment under an endo scope ora laparoscope, operation using needles forpercutaneous puncture, or manipulaters, and so on .

Micro machine technologies in the medical fieldare the follow ing 3 types.l) A w hole machine is a miniature size.2)An operation part of a tool is a miniature size and

operation action is small, but the size of acontroller or a power source is not a problem.

3)The size of a machine itself is not a problem, butoperation action of tool is small.In case of practical app lication of a medica l micro

machine, the size of machine is 10-3 - 10-4 meter.The machine whose size is 10-6 meter level is notrealistic, because of this size a machine does notproduce power.

3. Computer Aided Surgery System[l]3.1. Three Dimensional Medical Imagedimensional (3-0) organ structure of apatient in the CAS is reconstructed by using theinformation obtained from the X-ray CT, MRI,echography and so on. Three dimensionalreconstructed medical image system in the CASconsists of an image acquisition system, a dataprocessing system, and a graphic display. Allinformation from this CAS system is displayed ongraphical terminals. The reconstructed 3-D med icalimages are the most recognizable information for amedical doctor, and 3-D position data of tissuesinside the patient's body are the most important datato control surgical robots and mechatronics device s.Main applications to the CA S system are liver cancertreatment therapy, stereotaxic neuro-surgery,laparosucopic surgery, endosucopic surgery, andpartial liver transplantation.

Three

3.2. Surgical Robot[2]As a device to let operation instruments reach the

diseased part of a patient's body, robot technology isvery important. How ever, philosophy to develop asurgical robot is to assist a surgeon to overcome moredifficult procedures and thus help an incurablepatient as muc h as possible. There fore a surgicalrobot is a new hand of a surgeon, and it is not amachine to do the same action of a surgeon usingscissors or a scalpel.

The areas of medical robots are classified intotherapy, inspection, research,education and nursing(Table 1).

Table 1 Classification of Medical Robot

3.3. Safety ofMedical RobotThe robots for nursing, care and therapy(especially surgical robots) are quite different fromindustrial robots in the follow ing 4 aspects.1)The se robots contact hum an body directly.2)Functions required for these robots are different

according to their purpose; nursing, care,operation and therapy.

3)W hen these robots are used in practice, trialmovem ent or doing again are not allowed.4)These robots can be operated easily, even if anoperato r is not a specialist.In other words, safety of industrial robots keeps

dividing work areas between man and robots. Onthe other hand, the purpose of robots can not beachieved if these robots are not in contact with apatient or a cared person. The safety measu res

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against accidents should be considered from bothsides, hardware and software, and industrial robotsshould not be applied to these purposes.

Therefore, in order to develop therapy robots andnursing robots for practical use, it is veryimportanttodesign man-machine interface safely.But it becomes illogical that an airplane which cannot fly is the safest airplane, if one emphasize thesafety of the robots too much . Engineers shouldpursue safety and simple operation of robots to hisbest always using high technologies.

4. Clinical Application of the CAS4.1. Laser Surgery in Liver Cancer[3]

The first application of the CAS system is theresection and the spherical laser coagulationtreatment for liver cancer. Th e reconstructed 3-Ddata of liver by the CAS system are used to calculatethe best approach direction of the laser probe to avoiddamage of the large vessels in the liver. Th e resultof calculation is mapped on the surface of livermodel or the surface of patient's body model. Themapping on the patient's body is used to insert theneedle percutaneously under the guide of echographyor treatment w ith a manipulator for needle puncture.

The most suitable applications of micro machinein this therapy is a micro laser scanner on the end ofthe laser fiber needle. Big power is not necessaryfor this scanning of laser.4.2. Stereotaxic Surgery[4]Stereotaxic surgery is a kind of neuro-surgerywhich needs precise positioning of the surgicalapparatus and uses pre-determined locationinformation. It includes biopsy, injection ofmedicine, fiber scope laser surgery, radiant raytreatment and positioning of electrodes.

According to the positional information of thetumor(or any target) in the brain taken by the X-rayCT(or MRI) sliced images, the coordinates of theinstruments are set manually, and a cannulationneedle is inserted into the tumor. It is obvious thatintroduction of cannulation manipulator to thesurgery will provide more precise location of theneedle and make surgery safer. When the CASsystem is used for the cannulation of needle to braintumor, the optimum path of the needle toward thetumor is calculated so as not to damage the functionalarea of brain and the major brain vessels. Themanipulator inserts the needle to the tumor throughthe planned path.

Fig.1 A manipulator for percutaneously needle puncturecontrolled by the CAS system Fig.2 A manipulator for stereotaxic surgery controlled by

the CAS system

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Fig.3 X-ray CT image of cannulation to a phantom of waxgourd by a manipulator for stereotactic surgeryS.Conclusion

The applications of micro machine, mechatronicsand robotics in medicine are widely spread in clinicaluse. An expected area of medica l micro machine isminimally invasive surgery, especially laser radiationtherapy, stereotaxic surgery and laparoscopic surgery.As a new concept of robots and mechatronics system inmedicine, i t is necessary to integrate 3-D medicalimages and micro machine technology. By thisintegration, so far impossible or difficult surgicaltreatments will be enabled or facilita ted. At thebeginning of the next century, the CAS will makeprogress as the virtual reality micro surgery forminimally invasive therapy.

References[l]T.Dohi et al.; Computer Aided Surgery

System(CAS) -Development of SurgicalSimulation and Planning System with ThreeDimensional Graphic Reconstruction, 1 tConference on Visualization in BiomedicalComputing, IEEE, 458, 1990

[2]T.Dohi et al.; Robotics in Computer AidedSurgery System: Journal of Compuer AidedSurgery, Vol.1 No .l , 4, 1995

[3]D.Hashimoto et al.; Development of a Computer-

Aided Surgery System : Three-DimensionalGraphic Reconstruction for Treatment of LiverCancer, Surgery, 589, May 1991

-4IH.Nozaki et al.; Development of a ComputerAided Surgery(CAS) Sytem for NeurologicSurgery, Proc. of the 31st Conference of the JapanSoc.,ME&BE, vo1.30,532, 1992

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