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Journal Articles

Development of a laser processing head for the inspection and repair of damages inside of a half-inch pipe

Komatsu, Kazumi*; Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi*; Nishimura, Akihiko

Hozengaku, 16(3), p.89 - 95, 2017/10

no abstracts in English

Journal Articles

Laser therapy for twin-to-twin transfusion syndrome; Today and near-future

Yamashita, Hiromasa*; Oka, Kiyoshi; Yamanaka, Noriaki*; Seki, Takeshi; Kim, K.*; Kuwana, Kenta*; Masamune, Ken*; Naganawa, Akihiro*; Dohi, Takeyoshi*; Chiba, Toshio*

Nihon Reza Igakkai-Shi, 33(2), p.122 - 130, 2012/08

no abstracts in English

Journal Articles

Development of instrument and control device for a small intestine interal pressure

Naganawa, Akihiro*; Oka, Kiyoshi

Tateishi Kagaku Gijutsu Shinko Zaidan Josei Kenkyu Seikashu, 21, p.74 - 77, 2012/00

no abstracts in English

Journal Articles

A Novel ultrasmall composite optical fiberscope

Oka, Kiyoshi; Seki, Takeshi; Naganawa, Akihiro*; Kim, K.*; Chiba, Toshio*

Surgical Endoscopy, 25(7), p.2368 - 2371, 2011/07

 Times Cited Count:4 Percentile:25.4(Surgery)

We developed an ultrasmall composite-type optical fiberscope (1.1-mm diameter) with a central cauterizing laser fiber surrounded by imaging and illumination fibers as a tool for various surgical applications. Porcine mesenteric blood vessels were laser irradiated in vivo and the procedure was filmed using ultrahigh-speed (max 1,000,000 frames per second) and thermographic cameras. Blood flow was decreased by 81.7% after laser irradiation and the diameter of the vessels at the irradiated point was approximately 46-48% smaller than that of the unirradiated vessels. Medical doctors also confirmed that the blood vessel was blocked after the experiments. From these results, it was shown that this device is applicable to all medical regions.

Journal Articles

Self-tuning control of balloon internal pressure in ileus tube

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Yoshino, Junji*

Keisoku Jido Seigyo Gakkai Sangyo Rombunshu, 10(2), p.7 - 16, 2011/05

Enteroscopy was usually performed by the double balloon or capsule endoscopes. However, it is difficult to use these endoscopes in patients who suffer from intestinal obstruction and adhesion. We have developed a new endoscope that can be used in patients who suffer from these problems; the instrument consists of an ileus tube and an optical fiberscope (diameter 1.1 mm). The entire small intestine can be observed by controlling the internal pressure of the balloon in the ileus tube and by pulling the tube out at a constant speed. In our previous study, we developed an internal pressure control device that consists of a balloon attached to an ileus tube and a medical syringe. We also verified the control performance of this device. In this study, we have designed a new two-degrees-of-freedom control system having self-tuning capabilities that enhances the control performance for various types of syringes doctors use usually. The effects of the proposed method are illustrated by the experiment. The obtained results show that balloon pressure in the reference response satisfactorily tracks the output of the reference model and can be settled within $$pm$$2% in steady state. In addition, the disturbance rejection properties of the PID control method were affected by the changes in balloon pressure, but this problem can be solved by using the proposed control system.

Journal Articles

Control of balloon internal pressure for ileus tube using a syringe

Seki, Takeshi; Naganawa, Akihiro*; Oka, Kiyoshi; Ishikawa, Shinji*; Yoshino, Junji*

Nihon Kikai Gakkai Rombunshu, C, 76(766), p.1645 - 1647, 2010/06

Recently, by development of double balloon and capsule endoscopes, small intestinal whole area observation was enabled. However, it is difficult to use these endoscopes in patients with intestinal obstruction and adhesion. We developed a new endoscope that can be used in patients with intestinal obstruction and adhesion; this instrument consists of an ileus tube and an optical fiberscope (diameter, 1.1 mm). The complete observation of small intestinal is to be planned by controlling internal pressure of balloon in ileus tube, and pulling the tube out at constant speed. In our previous study, we have developed an internal pressure control device which consists of a balloon of ileus and an industrial cylinder, and we confirmed the utility. In this study, we developed a new control device combined with a general medical syringe, which enables to be sterilized easily and also to give less anxiety to patients. As the results of performance experiment of the device, the control accuracy was within $$pm$$0.5% error. Furthermore, in a disturbance response, the pressure fluctuation was limited down to 12%, compared with a case without any control.

Journal Articles

Development and basic study for lesion size measuring system on an endoscopic image

Oka, Kiyoshi; Seki, Takeshi*; Naito, Takehito*; Watanabe, Shinya*; Wakabayashi, Takao*; Naganawa, Akihiro*; Inui, Kazuo*; Yoshino, Junji*

Nihon Gazo Igaku Zasshi, 28(1), p.12 - 24, 2010/05

Focusing on the measurement function loaded on our rigid-typed endoscope for the fetal surgery treatment, we proposed that its combination with a generally used digestive endoscope enabled calibration of lesion size in stomach. While adding the function, with which the target size is to be easily measured, on the endoscope, we simplified the system structure as much as possible. We also tried to minimize the total cost by using the generally used endoscope, instead of making it from scratch. Combining another development, the composite-type optical fiberscope with diameter of 1.1mm, with a generally used endoscope, we proposed the following as the features: (1)acquisition of fiberscope image, (2)laser irradiation for treatments, (3)applying the real time measurement function of distance and blood flow by semiconductor laser to the generally used endoscope. We have operated the clinical study to the gastric wall of person with no health problem, using this system and confirmed it was available for practical use.

Journal Articles

Laser irradiation control of fetal endoscopic surgery for twin-twin transfusion syndrome; Verification of blood-flow interception by in vivo experiment

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Chiba, Toshio*

Keisoku Jido Seigyo Gakkai Sangyo Rombunshu, 9(10), p.70 - 75, 2010/04

The fetoscopic laser photocoagulation of chorionic plate anastomosing vessels is main treatment for the twin-twin transfusion syndrome. However, in this treatment, it is required highly endoscopic technologies, for example, blood flow measurement, estimation of distance between placental vessels and irradiation fiber tip and so on. We research and develop a composite-type optical fiberscope (2.2 mm in diameter), which has centrally-located cautery laser fiber and surrounding located fiberglasses for viewing. The laser transmitting efficiency of our fiberscope was very high (84.7%), and certain degree of cauterization was performed with from 20 to 40W laser power, when the distance between irradiated area and fiber tip was 10 mm. In addition, we emitted the laser to porcine liver for laser power control using a thermocouple as a basic research for intercepting placental blood flow, and we controlled the temperature of irradiation spot within $$pm$$0.3$$^{circ}$$C error in previous paper. In this study, we emitted the laser to in vivo porcine mesenteric vessel with blood flow for laser power control under temperature measurement. From the experimental result, the target temperature of 60 and 70$$^{circ}$$C with feedback control system using thermocouple was controlled low power of about 17W maintain target temperature within $$pm$$2.0$$^{circ}$$C error. Moreover, we measured the blood flow before and after laser irradiation by a laser Doppler blood-flow meter, and confirmed quantitatively the blood flow blocking.

Journal Articles

The Development of a composite-type optical fiberscope system for fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC)

Oka, Kiyoshi; Seki, Takeshi; Naganawa, Akihiro*; Yamashita, Hiromasa*; Kim, K.*; Chiba, Toshio*

Minimally Invasive Therapy and Allied Technologies, 19(2), p.94 - 99, 2010/04

 Times Cited Count:6 Percentile:33.02(Surgery)

We developed a new laser device using a composite-type optical fiberscope for laser surgery to treat twin-twin transfusion syndrome. The composite-type optical fiberscope (2.2 mm in external diameter) consists of a centrally located single fiber for laser treatment (0.1mm in diameter) and its surrounding fibers for diagnosis. This fiberscope enables transmission of 40-W Yb fiber laser. The Yb fiber laser can be focused to 10 mm focal length using two lenses on the tip of the fiberscope. In this research, we emitted the laser to in vivo porcine mesenteric vessel with blood flow both with an established laser fiber of 0.6-mm diameter (0.6-mm normal fiber) and with our composite-type optical fiberscope to compare the cautery performance of those devices.

Journal Articles

Internal pressure control of balloon for observation of a whole small intestine using an ileus tube type enteroscope

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Yoshino, Junji*

Nihon Kompyuta Geka Gakkai-Shi, 12(1), p.33 - 42, 2010/03

no abstracts in English

Journal Articles

Blood flow measurement system for fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC)

Seki, Takeshi*; Oka, Kiyoshi; Naganawa, Akihiro*; Yamashita, Hiromasa*; Kim, K.*; Chiba, Toshio*

Minimally Invasive Therapy and Allied Technologies, 18(6), p.350 - 355, 2009/12

 Times Cited Count:3 Percentile:17.42(Surgery)

Fetoscopic laser photocoagulation of chorionic plate anastomosing vessels (FLPC) applies to the treatment of previable fetuses with severe twin-twin transfusion syndrome (TTTS). However, there has not been an established method to confirm that the blood flow is blocked. For this issue, we have developed a composite-type optical fiberscope (2.2 mm in diameter). This fiberscope enables transmission of 50 W Yb fiber laser which can be focused to 10 mm focal length using two lenses on the fiberscope tip. In this study, we combined the fiberscope and a laser blood-flow meter, and irradiated cautery laser to porcine mesenteric vein with measuring blood flow at the same time. From the experimental results, we could quantitatively measure the blood flow before and after laser irradiation, and confirm the blood flow blocking with our system.

Journal Articles

Development of an instrument system for measuring the internal pressure of the small intestine using an ileus tube

Ishikawa, Noriko; Oka, Kiyoshi; Naganawa, Akihiro*; Yoshino, Junji*; Wakabayashi, Takao*; Watanabe, Shinya*; Naito, Takehito*

Nihon Kikai Gakkai Rombunshu, C, 75(756), p.2359 - 2361, 2009/08

Instruments for measuring the internal pressure of digestive organs are used for diagnosing functional diseases, judging how critical the condition is, and deciding the treatment method or determining the degree of alleviation. However, the technique wherein the internal pressure of the small intestine is measured is highly invasive and painful for patients, and the insertion of the catheter via transducers is not preferred because it involves the insertion of an electric instrument in the body. In this study, we developed a system that measures the pressure of the small intestine with an ileus tube, which is generally used for the treatment of ileus. The main feature of our system is that can be used to measure internal pressure without the insertion of electric instruments such as transducers into the body, allowing the assessment of ileus without causing pain to the patient being treated. In this note, we present a brief description of the structure and function of this instrument used to measure the internal pressure of the small intestine.

Journal Articles

Laser irradiation control of fetal endoscopic surgery for twin-twin transfusion syndrome; Performance verification using temperature sensor

Naganawa, Akihiro*; Oka, Kiyoshi; Suzuki, Katsumasa*; Seki, Takeshi*; Chiba, Toshio*

Keisoku Jido Seigyo Gakkai Sangyo Rombunshu, 7(8), p.53 - 59, 2008/07

no abstracts in English

Journal Articles

Composite-type optical fiberscope for laser surgery for twin-to-twin transfusion syndrome

Oka, Kiyoshi; Naganawa, Akihiro*; Yamashita, Hiromasa*; Nakamura, Tetsuya*; Chiba, Toshio*

Lecture Notes in Computer Science 5128, p.251 - 259, 2008/00

We present our new laser device for prospective human fetoplacental surgery including that of twin-twin transfusion syndrome. We developed acomposite-type optical fiberscope (2.2-mm in diameter) that enables transmission of 40-W Yb fiber laser light alongside of coaxial fetoscopic images. Using a laser condensing lens on the fiberscope tip, Yb fiber laser light can be focused 10-mm off. Using porcine liver tissue, despite changes in delivered laser energy, the diameter and depth of cauterized areas remained constant when the liver position agreed with the laser focal point, although the laser output altered the extent of tissue ablation. In conclusion, the performance of the fiberscope can be well controlled with accurate and efficient ablation of the target tissue. This Yb fiber laser fiberscope is expected to work much better if mounted on a miniature bending manipulator and if provided with additional functions (realtime distance and blood flow measurements).

Oral presentation

Advanced development of a laser endoscopy for FLPC of TTTS

Oka, Kiyoshi; Nakamura, Tetsuya*; Ueda, Hirohisa*; Toriya, Tomoaki*; Tsumanuma, Koji*; Naganawa, Akihiro*; Watanabe, Shinsuke*; Ishiyama, Akihiko*; Yamashita, Hiromasa*; Chiba, Toshio*

no journal, , 

no abstracts in English

Oral presentation

Design of balloon pressure control system for ileus tube

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Yoshino, Junji*

no journal, , 

no abstracts in English

Oral presentation

Quantitative evaluation of blood flow interception of fetoscopic laser irradiation control

Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Yamashita, Hiromasa*; Chiba, Toshio*

no journal, , 

We developed a new laser device using the composite-type optical fiberscope for laser surgery for twin-twin transfusion syndrome. A composite-type optical fiberscope (2.2 mm in diameter) consists of a centrally located single fiber for laser treatment and its surrounding fibers for diagnosis. This fiberscope enables transmission of 50-W Yb fiber laser. The Yb fiber laser can focus laser to 10 mm focal length using two lenses on tip of the fiberscope. In this paper, we describe the experimental results of temperature control during blood-flow interception of porcine mesenteric venous flow and measure blood flow before and after laser irradiation for evaluation blood flow interception.

Oral presentation

Development of minimally invasive laser device using composite-type optical fiberscope of 1.1 mm in diameter

Seki, Takeshi*; Oka, Kiyoshi; Naganawa, Akihiro*; Chiba, Toshio*

no journal, , 

During conventional endoscopic laser treatments, it is difficult to keep distance between target tissue and fiberscope tip for effective laser irradiation. Moreover, the choice of laser power and diagnosis of a successful procedure depend on the operator's skill or instincts. Therefore, we developed a new minimally invasive laser device using a 1.1 mm in diameter composite-type optical fiberscope (COF) to overcome the above problems. This device enables transmission of 50 W Yb fiber laser and an image in parallel. In addition, this COF enables the measurement of the blood-flow of target tissue and estimates of the distance between irradiation area and the fiber tip in real time by means of an embedded laser Doppler blood-flow meter. In this paper, we present a configuration of the minimally invasive laser device using the 1.1 mm COF and the results of the basic performance experiments.

Oral presentation

Development and usefulness of the optical fiberscope with a laser irradiation function of 1.1 mm of outer diameters

Oka, Kiyoshi; Seki, Takeshi*; Naganawa, Akihiro*; Chiba, Toshio*

no journal, , 

no abstracts in English

Oral presentation

Control of balloon internal pressure in an ileus tube by using a syringe

Ishikawa, Shinji*; Seki, Takeshi*; Naganawa, Akihiro*; Oka, Kiyoshi; Yoshino, Junji*

no journal, , 

no abstracts in English

28 (Records 1-20 displayed on this page)