The world's first precise model of the human paranasal sinus has been developed for ESS training.
Using this new model, the surgeon can practice the surgical techniques necessary for successful endoscopic sinus surgery (ESS) without the use of cadavers.
- The National Institute of Advanced Industrial Science and Technology (AIST) has developed the world's first precise model of the human paranasal sinus for training in endoscopic sinus surgery (ESS).
- ESS is not as common as other surgical techniques such as abdominal surgery (laparoscopy), since the intranasal structure is very complex, and training opportunities using cadavers are decreasing.
- For this model, AIST has developed materials and structures that provide tactile perceptions that are similar to the human body. This makes it possible for the surgeon to practice surgical techniques that are nearly equivalent to those acquired with cadavers.
- Constructing an operating area for incision and resection with replaceable parts has minimized training costs for this surgical model.
- Being X-ray CT compatible, this model can also be useful for training of surgical navigation systems.
- This model should contribute to an increase in ESS with improved safety.
The Institute for the Human Science and Biomedical Engineering (HSBE; Director: Dr. Shinya Saida) at the National Institute of Advanced Industrial Science and Technology (AIST; President: Dr. Hiroyuki Yoshikawa), has produced a precise human paranasal sinus that is modeled experimentally for surgical skill training in endoscopic sinus surgery (ESS). Given an excellent endoscopic interior view of the sinus, the surgeon can practice basic surgical techniques, such as cutting and removing tissues (Ethmoidectomy, Sphenoidectomy through the ethmoidal sinus, opening the natural ostium of the maxillary sinus, etc.), using actual surgical instruments (e.g., forceps) with a realistic tactile perception for this model.
While minimally invasive endoscopic surgery is a benefit for the patient, there are some disadvantages such as significantly restricted vision through the endoscope. Handling of instruments with limited mobility requires the surgeon to acquire a higher level of surgical skills. The surgeon requires intensive training and experience to acquire the necessary quality surgical skills. This is particularly true when operating on the paranasal sinuses, due to its complex structure and its location adjacent to vital organs. The vital organs, the optic nerve, the brain, and arteries, are separated only by very thin bone walls.
As for laparoscopic surgery, training is possible using animals or artificial models, so endoscopic procedures are more popular. For the paranasal sinus, however, no appropriate animal model is available and it was impossible to produce an anatomical model due to the complex structure and the fragility of this organ. Training therefore has had to rely on the use of cadavers, which are extremely rare. As a result, endoscopic procedures are not as common as with other parts of the body.
The model developed by HSBE precisely reproduces the bone structure, based on the CT images of the human nose, using materials and structures that were also developed by HSBE. This model provides tactile perceptions that are similar to real tissue. This enables the surgeon to practice endoscopic surgical techniques that are nearly equivalent to those acquired with cadavers. Making the operating area for incision and resection out of replaceable parts has minimized training costs for the model.
We expect this model to contribute greatly to the spread of endoscopic sinus surgery with improved safety. This technique will complement training opportunities that have been declining with the decreasing supply of cadavers and promote the acquisition of basic surgical techniques. This model is scheduled to be displayed at the 104th meeting of the Oto-Rhino-Laryngological Society of Japan (Held on May 22nd and 24th, 2003 at Nihon Toshi Center, Tokyo). THe model has been commercialized by SurgTrainer, Ltd. (President: Mr. Suehiko Kikuchi), a certified AIST venture company established by the developers, since 2004 June, in cooperation with KOKEN Co., Ltd. (President: Dr. Teruo Miyata), a joint research partner on this project.
Background and History of Research
Why does the AIST perform this type of research?
The HSBE of the AIST is conducting research on technology to support minimally invasive surgery. This research is conducted, examining the human interface in the Research and Development Project of Medical and Welfare Equipment Technology titled "Advanced Support System for Endoscopic and Other Minimally Invasive Surgery (2000-2004)" (*1). One of the major themes of this project is research on improving the environment for training and rehearsing surgery. Under this theme, Research and Development of a surgical training system is an objective parameter for the surgical skill assessment. This is based on physical quantities that are being advanced to make sufficient preoperative training possible, primarily for endonasal surgery. The model presented here is a result of these activities.
Why Has Such a System Not Yet Been Realized?
- (1) Since the paranasal sinus structure is very complex, preparation of these models by conventional casting techniques was practically impossible.
- (2) Once they are reconstructed on a computer as three-dimensional (3D) shape data, complicated structures can usually be reproduced as 3D models by the use of a rapid prototyping (RP) techniques, typically by optical-molding.
However, the bony walls that constitute the paranasal sinuses are very thin (about 0.1mm), and the reconstitution of their 3D structure is difficult; even with the use of CT images with improved resolution (about 0.4-0.5mm).
- (3) Since characteristics of materials that can be handled with an RP system are very different from those of biological tissues, it is difficult to reproduce the tactile responses that the surgeon feels during surgery with RP technology.
- (4) Although research and development of surgical simulators that incorporate virtual reality (VR) technology are rapidly advancing, the algorithm for organ deformation that is associated with surgical manipulation and the technology to present these responses to our sense of touch and pressure (technology for presentation of tactile and force sensations, called haptics) are still in the developmental stage. In particular, real-time calculation or feedback of resecting thin bones, such as opening of the ethmoid sinus, is impossible at the present time.
Where Will Such Technology be Useful?
Acquiring adequate surgical skills are based on an understanding of the complex structures inside the nasal cavity and sinuses. Surgeons, through training using this model, will acquire significant improvements in their physical skill level, and contribute to the spread and safety of minimally invasive surgery.
Research Contents (Performance of the Developed Technology)
Differences from Conventional Technology
Generally, models of the human body are for "observation", and their exterior or interior is not constructed so that it can be "operated" by surgical procedures. These models are also expensive to manufacture so that they are not usually cut or drilled by surgical instruments. This model has been developed primarily for training in surgical procedures, and it is designed to reproduce not only the morphology but also the tactile feeling that occurs during surgery.
Compared with recent operation simulators that have been developed using VR technology, our model is superior in the quality of tactile responses and the feeling that it gives during live performance, despite its low price.
The skeletal and mucosal structures of this model are reconstituted from CT images of the human body and they can tolerate endoscopic examination. The internal structure of the ethmoidal sinuses are also reproduced. For this reason, the model enables the training of surgeons in surgical procedures using actual surgical instruments (including forceps) possible while allowing them to feel near-real tactile responses of the body. Also, as the parts of the model that are removed or cut during training are designed to be replaceable, the cost of training can be minimized.
The model is CT compatible and suitable for image guided surgery training as well.
How Has It Become Possible?
- (1) The 3D structure of the skeleton was precisely reproduced by RP technology.
- (2) The 3D CAD data of the model, that could be reproduced by RP technology, was reconstructed not only from CT images but also from anatomical findings with the cooperation of skilled surgeons.
- (3) To realize both the precise morphology and tactile responses as close to those of the live tissue, many kinds of materials and structures were evaluated by sensory tests of skilled surgeons. Finally, we found that a combination of RP material and resin coating gives the best result.
- (4) Since it is a real model, this system allows real-time feedback of tactile responses and the feeling of tissue resection.
We intend to develop this model into a more advanced ESS surgical skill training system by combining it with a measurement and presentation system for data related to surgical operations (force applied to the patient, position of the endoscope, etc.). This system is being developed as a part of the research project mentioned above.
Patient responses, such as pain, blood pressure, pulse, perspiration, etc., are being studied at the Digital Human Research Laboratory of the AIST. Such knowledge will be combined into the developed model in the near future, to add even more reality to the surgical training system.
Applying the technology to build precise models to other parts of the body is also planned.
TOP LEFT: The whole view of a precise model of the human sinus (primary test piece). It has been named "SurgReady" (TM)
RIGHT: Opening the natural ostuim of the maxillary sinus (ABOVE). After making an incision with a scalpel (BELOW), the interior of the maxillary sinus is observed through the exposed natural opening.
BOTTOM: Ethmoidectomy. (LEFT) The right ethmoidal sinus is approached from the front using forceps. (MIDDLE) The posterior part is being exposed.
LEFT: Forceps for ESS.
RIGHT: Rigid endoscopes for ESS. About 20cm long, 4mm in diameter. Viewing angles are 0, 30, 45, 70, etc. degrees.
The model in use with a surgical navigation system "Evans". It is X-ray compatible. (Courtesy of Prof. Koichi Tomoda (Dept. of Otolaryngology, Kanazawa Medical University, Kanazawa, Japan) and Tomiki Medical Instruments, Co., Ltd. (Kanazawa, Japan) .)
(*1) This project was started in 2000 by the Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, Ministry of International Trade and Industry (Presently the AIST) and the New Energy and Industrial Technology Development Organization (NEDO) (Chairperson of the Board of Directors: Chikara Makino). As research organizations that belonged to the Agency of Industrial Science and Technology became independent agencies, the part of the project assigned to the national research organizations has been taken over by the HSBE of the AIST.
- Paranasal Sinuses :
Cavities located behind the face in the skull are separated by thin bony walls. Chronic sinusitis is a condition in which spontaneous discharge of fluids that has accumulated in the paranasal sinuses by the cilia has become impossible. It is an indication for surgical treatment.
- Minimally Invasive Surgery :
"Invasiveness" is the term that represents the physical stress that medical actions inflict on the patient. Cutting healthy tissues to reach the target organ located deep in the body for surgery or examination is "invasive". Compared with conventional surgery, in which a wide incision is made on the body surface, endoscopic surgery, which can be performed with a small surgical wound, is described as "less invasive" or "minimally invasive".
- Rapid Prototyping (RP) Technology :
Technology to reproduce 3D morphology from 3D shape (CAD) data on a computer by serially stacking up its sections as thin layers. It may be accomplished by various methods including optic molding, powder sintering, and thin-plate layering.
[References: RP Industry Association Japan: http://www.rpjp.or.jp/ ]
Senior Research Scientist
Human-Computer Interaction Group
Institute for Human Science & Biomedical Engineering
National Institute of Advanced Industrial Science and Technology (AIST)
Tsukuba Central 6
1-1-1, Higashi, Tsukuba, Ibaraki 305-8566, Japan
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Last updated : August 12, 2004