Computer

Surgical Advanced

Instruments Hand

Fig. 1. Computer-aided surgery advanced technologies with surgical robots, three-dimensional medical images, etc., based on computer technology. This new surgical field is called computer-aided surgery (CAS) [1]. The reconstructed three-dimensional medical images provide the most recognizable information for medical doctors and advanced visualization for surgeons. Surgical robots function as advanced hands for surgeons. The advanced vision and hands available to surgeons are creating a new surgical environment (Fig. 1).

Advanced Vision

Usually, medical images in a surgical field are used mainly for diagnosis before and after the operation. Computer graphics technology visualizes the three-dimensional structure of organs, vessels, and tumors using information from X-ray computed tomography (CT), magnetic resonance imaging (MRI), echog-raphy, and so on. The main fields of research on three-dimensional medical images in CAS are the acquisition system, the reconstruction method, multi-modality matching, and three-dimensional display.

Three-Dimensional Display

There are three kinds of display methods for three-dimensional image:

Pseudo-three-dimensional display. Basically, this display is a two-dimensional display. A stereoscopic feeling is obtained by rotating a three-dimensional model on a two-dimensional display. As three-dimensional models, there are the voxel model and the surface model.

Binocular stereoscopic display. This method uses two two-dimensional images for binocular vision. The feeling of depth is provided mainly by binocular parallax and convergence. However, the absolute three-dimensional position cannot be given. Since observation by this method is not physiological, observation for a long time causes visual fatigue. As displays of this method, there are a stereoscope, a parallax stereogram, and a three-dimensional lenticular sheet.

True three-dimensional display. The true three-dimensional display produces a three-dimensional image in real three-dimensional space. As displays of this method, there are holography, integral photography (IP), and volume graph based on the principle of IP. Since observation by this method is physiological, this observation does not cause visual fatigue. Absolute three-dimensional positions and motion parallax are given. IP projects three-dimensional models using a two-dimensional lens array called a "fly's eye lens (FEL)" and a photographic film. Recently, a computer-generated IP called integral videogra-phy (IV) has been developed by FEL and color liquid crystal display (Figs. 2 and 3) [2]. IV can display full-color video. The volume graph and IV give absolute three-dimensional positions and they are much simpler than holography, which uses interference of laser light. They can project the reconstructed 3D model at geometrically exact position in internal cavity with relatively minimal computation and engineering effort. Therefore they are very suitable for three-dimensional display for surgical navigation.

Table 1 compares the binocular stereoscopic image and the true three-dimensional image for surgery.

Fig. 2. Binocular stereoscopic display (left) and true three-dimensional display (right)

/

Ü

"g

1/ _y\_\

Fig. 2. Binocular stereoscopic display (left) and true three-dimensional display (right)

Calculation by Imaginary Screen

Voxel Data

Imaginary Fly's Eye Lens

Voxel Data

Imaginary Fly's Eye Lens

H.D. Projector or LC Display

Screen

Projected 3-D Image

Projected 3-D Image

H.D. Projector or LC Display

Screen

Fly's Eye Lens (2-D micro convex lens array)

Fig. 3. Integral videography. HD, high definition; LC, liquid cristal

Table 1. Comparison between binocular stereoscopic image and true three-dimensional (3-D) image for surgery

Binocular

True 3-D

Image

Fineness

Excellent

Good

Processing

Simple

Complicated

Special glasses

Necessary

Unnecessary

3-D Rec.

Parallax

Fixed

Physiological

Convergence

Fixed

Physiological

Accommodation

Fixed

Physiological

3-D position

Only feeling

Absolute position

Visual fatigue

Inevitable

Free

Number of observes

Limited

Not so limited

Suitable application

Intraoperative

Percutaneous

navigator

Advanced Hand [3]

The typical advanced hand for surgeons is a surgical robot. The surgical robot is one of the medical robots and has the problems common to medical robots. Medical robots are quite different from industrial robots in the following four aspects:

These robots contact the human body directly.

The combination of surgical maneuvering differs by cases; modifying the combination to adopt to patients' condition is necessary. When these robots are used in practice, trial movement or redoing is not allowed.

These robots can be operated easily even if the operator is not a specialist.

Safety of Medical Robot

Safety of industrial robot is guaranteed by maintaining the gap between the robot and the human. This approach is not applicable to medical robot where robots contact the patient (human.) Therefore, the safety measure should be taken from both software and hardware aspects in medical robotics, where the measure is taken mostly hardware configuration in industrial robotics.

Medical robots must be designed so that a user can cope easily when the robot causes trouble. There are four kinds of emergency actions, and which action to adopt differs according to the kind of surgical robot:

Stop in the position where an emergency happened (= Freeze).

Move to the original or specified position automatically.

Escape to the safe position automatically in case of emergency, then to arbitrary position after emergency. Move to the arbitrary position manually.

Classification of Surgical Robots

An advanced hand for a surgeon is one of the medical instruments, and it is called a surgical robot or therapeutic robot. There are two kinds of surgical robots for CAS, the navigation robot and the treatment robot. Three-dimensional medical images during an operation by surgical robots are very important.

Navigation robot. Navigation robots are percutaneous needle punctures, cannulations, and others. Safety and minimally invasive navigation to a diseased part are very important to achieve a good result from a surgical operation. It is especially important for this robot to access the complicated parts that cannot be accessed directly by the surgeon.

Treatment robot. These robots are required to have functions of cutting, resection, exfoliation, suture, ligation, and others. However, these functions should be designed in the mechanism, which is suitable for mechanical operation. The robot should be designed specifically to achieve these surgical maneuvering instead of re-using general purpose robot.

Principles of Design of Medical Robots

Surgical operations have developed with the skillful use of the surgeon's hands and eyes. Many surgical operations are not suitable for performance by a machine. Moreover, a machine that performs the same action as a surgeon cannot perform treatment better than a surgeon. Therefore, a surgical robot does not just imitate the surgeon's action, but it must be designed in consideration of the following points:

It should be designed corresponding to the purpose of treatment. Robot should be designed to best achieve the targeted surgical maneuvering which otherwise is less effective by manual maneuvering.

It should provide better treatment than the current treatment provided by the surgeon's eyes and hands. It should make the most of the current knowledge and experience of the surgeon.

Development Situation in Japan

Navigator of a Laparoscope

As an application of robotics to laparoscopic surgery, a navigation robot system for laparoscopy with a CCD camera has been developed. It is required that this kind of navigation robot should be safe at all times. It is especially important that neither the abdominal wall nor the internal organs of the patient be damaged. This problem is solved by combining a planar five-bar linkage mechanism and a fixed ball joint placed on the abdominal wall (Fig. 4) [4]. In Japan, it has been developed and marketed under the brand name Naviot. This navigator fulfills the important conditions of the surgical robot. It has the following features as compared with other navigators:

There is no danger of damaging the abdominal wall and internal organs. The operation area on the abdomen is very wide.

The drive section and the five-bar linkage mechanism section can separate easily. Washing and sterilization of the five-bar linkage section are very easy. Operation by the surgeon himself or herself is very easy.

A novel robotic endoscope system has also been developed. It can be used to observe a wide area without moving or bending the endoscope. The system con-

Fig. 4. Naviot navigator of laparascope

Automatic Zoom component

Automatic Zoom component

i > simple and small mechanism

Fig. 5. Construction of the wide-range endoscope system using wedge prisms. CCD, charge-coupled device sists of a laparoscope with zoom facility and two wedge prisms at the tip (Fig. 5) [5].This new concept produces the following excellent characteristics. First, it can change the field of view even in a small space. Second, it is safe because it avoids the possibility of hitting the internal organs. Finally, because it does not require a large mechanism for manipulation of the endoscope, it does not obstruct the surgeon's operation. During evaluation, it was confirmed that the range of view and levels of image deformation were acceptable for clinical use.

In order to keep a treatment spacein the abdomen, a gasless method for lifting the abdominal wall by subcutaneous wiring has been developed in Japan [6].This method has several merits compared with the pneumoperitoneum method. When robot technology is applied for laparoscopic surgery, the abdominal wall-lifting method is far better than the pneumoperitoneum method.

Stereotaxic Surgery

Stereotaxic surgery is a kind of neurosurgery that requires precise positioning of the surgical apparatus, using predetermined location information. According to information on the position of the tumor (or any target) in the brain obtained by X-ray CT (or MRI) sliced images, the coordinates of the instruments are set manually, and a cannulation needle is inserted into the tumor. We have developed a cannulation manipulator to cooperate with the CAS system. This manipulator has 6 degrees of freedom. The needle is inserted to the target position according to the precalculated direction by specifying the parameters of the freedoms. All components of the manipulator are designed to fit the size of the opening of the CT scanner. The manipulator has a safety-oriented design and compactness. When the CAS system is used for cannulation of the needle to the brain tumor, the optimal path of the needle toward the tumor is calculated so as not to damage the functional area of the brain and the major brain vessels. The manipulator inserts the needle to the tumor through the planned path. This manipulator can also be used for X-ray CT-guided stereotaxic surgery.

Ultrasound computed tomography (USCT) for neurosurgery was also developed in 1995 [7]. USCT reconstructs arbitrary planes from multiple scans taken during rotation of the probe.

A three-dimensional overlay system for neurosurgery called the volumegraph has been developed (Fig. 6). The volumegraph is a sheet that has recorded a three-dimensional image before the operation, and this image is observed without special glasses. In September 1996, the first operation using this system was successfully performed at Tokyo Women's Medical College.With this system, the medical doctors can confirm the target position before opening the head, and it is easy to decide the access point and the opening area of the head [8]. The integral videography system is now used for neurosurgery [9].

Stem-Cell Harvesting Manipulator [10]

A stem-cell harvesting manipulator system has been developed in my laboratory. This device efficiently harvests bone marrow for transplantation with the use of a newly developed passive flexible drilling unit and suction mechanism. The device reduces the invasiveness of bone marrow harvesting by collecting stem cells from the iliac bone with minimal punctures and by reducing opera-

3-D display

Half-mi

ierator

Fig. 6. Navigation system by superimposition

Mucous membrane Incision

Cutter V s;

Balloon V.._ Prostata catheter Bladder

Mucous membrane Incision

Cutter V s;

Perfusate Perfusate

Perfusion pipe

^Drill

Prostate tissue

Roller pump Cutter

^Drill

Fig. 7. End-effector with 3 degrees of freedom: arm, cutter, and drill tion time and contamination by T-cells. The device is inserted into the medullary space from the iliac crest and aspirates the bone marrow while an end mill on the tip of the drilling unit drills through the cancellous bone to create a curved path (Fig. 7). In vitro and in vivo pig studies showed that the device can be inserted into the medullary space of the pig iliac bone and used to harvest about six times as much bone marrow per puncture as the conventional aspiration method. The studies also showed that the device can generate higher and longer negative pressure than the aspiration method. The device, when applied in clinical study, will reduce invasiveness by harvesting a denser graft from a wider area of the iliac bone compared with the conventional aspiration method, although minimal puncturing is required.

Transurethral Resection of the Prostate (TURP) [11]

Currently, transurethral resection of the prostate (TURP) is the gold-standard treatment and the most common surgical procedure for benign prostatic hyper-plasia (BPH). However, damage to the mucous membrane of the urethra and extended surgery lead to complications. In order to resolve these problems, we have proposed a new prostatectomy and developed a TURP manipulator that has a prostate displacement mechanism and a continuous perfusion-resection mechanism (Fig. 8).This manipulator has 3 degrees of freedom: bending an arm, translating a cutter, and rotating a drill at the end effector. The arm enters and bends the prostate; the cutter is then inserted into the enlarged prostate, the drill cuts the enlarged tissue into small pieces, and a pump removes them by suction. The mechanism can resect the prostate quickly without damaging the mucous membrane.

Stem cell harvesting manipulator

Bone marrow needle

Flexible drilling unit

Stem cell harvesting manipulator

Bone marrow needle

Flexible drilling unit

Fig. 8. Concept of the stem-cell harvesting manipulator

Forceps Manipulator with a Bending Mechanism [12]

A new endoscopic hand-held forceps manipulator for endoscopic surgery using two bending mechanisms by multislider linkage mechanisms to achieve high mechanical performance and applicability has been developed in our laboratory. One bending mechanism is for horizontal plane bending, and the other is for vertical plane bending, enabling 2 degrees of freedom of independent motion between ±90° and +90°. To realize the bending of the top of the forceps, the multislider linkage mechanism is superior to the wire-driven mechanism. The bending mechanism consists of three outer frames, two rotating joints, and two sliding linkages for drive and restraint. Two pin joints can each rotate ±45°, enabling rotation of ±90°. Rotation of the joint is accomplished by pulling or pushing the adjacent element by sliding linkage in order (Fig. 9). An in vivo experiment showed that this manipulator performed endoscopic surgical tasks under the pneumoperitoneum and was confirmed as easy to operate.

Conclusions

Applications of three-dimensional images and robotics in medicine are widespread in clinical use. As a new concept of robot systems in medicine, it is necessary to integrate with three-dimensional imaging technologies. By this integration, surgical treatments so far impossible or difficult will be enabled or facilitated. Medical robots and three-dimensional medical images provide advanced hands and vision for surgeons; in the 21st century, these new devices for surgeons will develop new surgical fields, such as virtual reality microsurgery, telesurgery,

Fig. 9. Multi-degree of freedom (DOF) end-effector with 2-DOF bending mechanism and 1-DOF forceps mechanism

Fetus Surgery

Middle-aged Elderly

Fetus Surgery

Cancer, Cardiovascular System Disease, etc.

•Micro robot for Surgery •3-D Medical Image for Surgery •Micro/Nano Bio-mensuration

•Robot for Surgery

•3-D Medical Image for Surgery

•Micro robot for Surgery •3-D Medical Image for Surgery •Micro/Nano Bio-mensuration

Spinal Injury

(Traffic Accident)

Spinal Injury

(Traffic Accident)

Regenerative Medicine

Rehabilitation Robot

Regenerative Medicine

Rehabilitation Robot

Neuro-Informatics Therapy (Regeneration and Reconstruction of Neuro-Network)

Fig. 10. New robotic surgery fields for disabled persons. MIT, Minimally invasive therapy; QOL, quality of life fetal surgery, neuroinformatics surgery, and others (Fig. 10). However, engineers who develop medical instruments should be reminded that the clinical environment is quite different from the industrial one, and should develop clinically oriented devices instead of just applying industrial robots.

References

1. Dohi T, Ohta, Y, Suzuki M, Chinzei K, Horiuchi T, Hashimoto D, Tsuzuki M (1990) Computer aided surgery system (CAS) -development of surgical simulation and planning system with three dimensional graphic reconstruction. 1st Conference on Visualization in Biomedical Computing, IEEE, 458

2. Nakajima S, Kobayashi E, Orita S, Masamune K, Sakuma I, Dohi T (1999) Development of a 3-D display system to project 3-D image in a real 3-D space. Proceedings of 3D Image Conference '99, 49-54, Tokyo, Japan

3. Dohi T, Hata N, Miyata K, Hashimoto D,Takakura K, Chinzei K, Yamauchi Y (1995) Robotics in computer aided surgery system. J Computer Aided Surg 1(1):4-10

4. Kobayashi E, Masamune K, Suzuki M, Dohi T, Hashimoto D (1996) Development on a laparoscope navigator using a planar five-bar linkage. Proceedings of 5th Conference of Japan Society of Computer Aided Surgery, 77-78

5. Kobayashi E, Masamune K, Sakuma I, Dohi T (2000) A wide-angle view endoscope system using wedge prisms. Medical Image Computing and Computer-Assisted Inter-vention-MICCAI 2000, 661-668

6. Hashimoto D, Nayeem SA, Hoshino T (1995) Advanced techniques in gasless laparo-scopic surgery. World Scientific Publishing, Singapore

7. Hata N, Suzuki M, Dohi T, Takakura K, Iseki H, Kawabatake H, Yamauchi Y, Umaki K (1994) Ultrasound CT, Image technology & information display, 94-OCT, 1194-1198

8. Yamane F, Iseki H, Masutani Y, Iwahara M, Nishi Y, Kawamura H, Tanikawa T, Kawabatake H, Taira T, Suzuki M, Dohi T, Takakura K (1995) Three-dimensional image guided navigation with function of augmented reality. Proceedings of 4th Conference of Japan Society of Computer Aided Surgery, 99-100, Tokyo, Japan.

9. Liao H, Nakajima S, Iwahara M, Hata N, Sakuma I, Dohi T (2002) Real-time 3D image-guided navigation system based on integral videography. Proceedings of SPIE Vol 4615, pp 36-44, San Jose, California

10. Ohashi K, Hata N, Matsumura T, Ogata T, Yahagi N, Sakuma I, Dohi T (2003) Stem cell harvesting device with passive flexible drilling unit for bone marrow transplantation. IEEE Trans Rob Autom 19:810-817

11. Hashimoto R, Kim D, Hata N, Dohi T (2003) A transurethral prostate resection manipulator for minimal damage to mucous membrane. Proceedings of the 6th Annual International Conference on Medical Image Computing and Computer Assisted Intervention, MICCAI 2003, LNCS 2878. Springer, pp 149-157, Montreal, Canada

12. Yamashita H, Kim D, Hata N, Dohi T (2003) Multi-slider linkage mechanism for endoscopic forceps manipulator. Proceedings of the 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003), Vol 3, pp 2577-2582, Las Vegas, Nevada, U.S.A.

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