齊藤 一幸

In recent years, various types of medical applications of microwave energy have widely been investigated and reported. We present a surgical device which employs the thermal effect produced by microwave energy. High power microwave energy can generate a coagulated region at the surface of the biological tissue such as organs. By coagulating organs, bleeding can be stopped. However, a microwave surgical device cannot cut the tissue without any device support, such as a blade. On the other hand, radio frequency (RF) current capable of cutting tissue without any support. This study presents a combination of a forceps type microwave surgical device combined with RF current for biological tissue cutting mechanism. Furthermore, ten sealed porcine blood vessels, sealed by the device, capability to withstand pressure were measured. Sealed blood vessels can withstand up to 200 mmHg of pressure and sufficient to withstand human blood pressure.

Recently, various electromagnetic (EM) applications have become common, and humans are frequently exposed to EM waves. Therefore, the effect of EM waves on the human body should be evaluated. In this study, we focused on the specific absorption rate (SAR) due to the EM waves emitted from a smartphone, developed high-resolution numerical smartphone models, and calculated SARs under various conditions.

Low frequency communication such as MHz band communication is a feasible method to reduce signal attenuation from the human body, although slow data rates limit its range of applications. In this paper, we designed two coil antennas for wireless capsule endoscopic (WCE) medical image transmission, including a small-sized dual-band transmitting antenna that can be placed inside the WCE and a corresponding receiving antenna that can be mounted on the abdomen of the human body. The proposed antennas can be fed by a battery-powered impulse radio transceiver that contains five signal peaks in the MHz band, and two signal peaks (38.5 and 57.6 MHz) are selected for antenna design to realize dual-band communication with higher data rates. Dimensions of the transmitting antenna and the receiving antenna are π × (5.5)2 × 2 mm3 and π × (40)2 × 4.8 mm3 , respectively. The antenna distance that satisfies the WCE medical image transmission requirements is roughly estimated by the received power from the transceiver. With the antenna distance of 50 mm, the attenuation is 33 and 47 dB at 38.5 and 57.6 MHz, respectively. With the antenna distance of 100 mm, the attenuation is 39 and 59 dB at 38.5 and 57.6 MHz, respectively. It can be estimated that proposed antennas can realize a total data rate of 2.5 Mbps within 100 mm antenna distance if two antennas are aligned or within 50 mm antenna distance if two antennas are misaligned to 60 mm.

Multi-band communication is a viable method to realize a higher antenna transmission speed for MHz band wireless capsule endoscopic (WCE) communication. However, due to the strict size limitations of capsules, it is difficult to design compact multi-band transmitting antennas. In this paper, a single-coil dual-band transmitting antenna is proposed. By optimizing the matching circuit of the antenna, two resonant frequencies can be generated from one coil, thereby reducing the size of the antenna. The simulated reflection coefficient shows that the two resonant frequencies of the antenna are 38.5 and 57.6 MHz, respectively. The simulated transmission coefficient indicates that the antenna can be used for WCE communication in the MHz band.

Combination of hyperthermia and radiation therapy for treatment of tumors is effective. When heat is applied to tumor tissue, the tumor cells become more oxygenated, which in turn makes the cells radiosensitive. Thus, by combining the heat with radiation, lower levels of radiation can be achieved due to this increased radiosensitivity. Blood works as a temperature regulator within our bodies, making it difficult for tumors to maintain higher temperatures for a long period of time. The purpose of this research is to investigate the blood flow effect on hyperthermia by means of microbiological investigations, as well as technical experiments, computer simulations, and mathematical calculations.

Wireless capsule endoscope (WCE) is a device that can realize real-time image transmission without cables. In this paper, a tri-band WCE communication system is proposed for low frequency real-time image transmission. The system consists of two transmitting antennas and a receiving antenna, with three frequency bands (38.5, 48.2 and 57.6 MHz band). Simulated results show that the path loss is 51, 30.6 and 54.4 dB at 38.5, 48.2 and 57.6 MHz with the distance of 50 mm between the capsule and the receiving antenna, and indicating that the communication system is possible to be used for WCE real-time image transmission.

In this paper, two printed coil antennas for wireless capsule endoscopic (WCE) communication system are proposed. Diagnostic images taken by WCE cameras are sent to an external device and displayed simultaneously. Two resonant frequencies of the proposed antenna are 38.5 and 57.6 MHz. Due to low resonant frequency, signal attenuation inside human body can be decreased, compared to a WCE antenna operating at Medical Implant Communication Systems (MICS) band (402-405 MHz). The receiving antenna size is 64×64×1.6 mm 3 , and the transmitting antenna is 10 mm in diameter and 2 mm thick. A human equivalent phantom is used to evaluate the influence of human body. In addition, the communication link sensitivity with different locations, orientations and misalignments are discussed.

<p>Nowadays, mobile communication technology has become essential; thus, it is important to consider the effect of electromagnetic radiation from mobile terminals such as smartphones on the human body. In this study, we calculated the specific absorption rate (SAR) and temperature increase in pregnant women exposed to a smartphone's radiation at 13, 18, and 26 weeks of gestation. The results indicate that the SARs were much lower in fetuses than in pregnant women under all of the calculation settings in this study. Moreover, the maximum temperature increases in fetuses were half of those in pregnant women.</p>

We have been working on the development of a PET insert for existing magnetic resonance imaging (MRI) systems for simultaneous PET/MR imaging, which integrates radiofrequency (RF)-shielded PET detector modules with an RF head coil. In order to avoid interferences between the PET detector circuits and the different MRI-generated electromagnetic fields, PET detector circuits were installed inside eight Cu-shielded fiber-reinforced plastic boxes, and these eight shielded PET modules were integrated in between the eight elements of a 270-mm-diameter and 280-mm-axial-length cylindrical birdcage RF coil, which was designed to be used with a 3-T clinical MRI system. The diameter of the PET scintillators with a 12-mm axial field-of-view became 255 mm, which was very close to the imaging region. In this study, we have investigated the effects of this PET/RF-coil integrated system on the performance of MRI, which include the evaluation of static field (Bo) inhomogeneity, RF field (B1) distribution, local specific absorption rate (SAR) distribution, average SAR, and signal-to-noise ratio (SNR). For the central 170-mm diameter and 80-mm-axial-length of a homogenous cylindrical phantom (with the total diameter of 200 mm and axial-length of 100 mm), an increase of about a maximum of 31ST in the Bo inhomogeneity was found, both in the central and 40-mm off-centered transverse planes, and a 5 percentage point increase of B1 field inhomogeneity was observed in the central transverse plane (from 84% without PET to 79% with PET), while B1 homogeneity along the coronal plane was almost unchanged (77%) following the integration of PET with the RF head coil. The average SAR and maximum local SAR were increased by 1.21 and 1.62 times, respectively. However, the SNR study for both spin-echo and gradient-echo sequences showed a reduction of about 70% and 60%, respectively, because of the shielded PET modules. The overall results prove the feasibility of this integrated PET/RF-coil system for using with the existing MRI system. (C) 2017 Elsevier Inc. All rights reserved.

組織内加温法と小線源治療との組み合わせは，腫瘍の治療に有効であることが示されている．腫瘍の温度を上昇させることにより，その腫瘍は放射線に対して敏感になるため，結果として放射線量を低減させることが可能である．本研究の目的は，深在性の乳房腫瘍に対して効果的に加温可能な侵襲型アプリケータを選定し，これにより腫瘍部の温度を42.5&deg;C以上に上昇させ，30 Gy未満の低線量放射線の効果を調べることである．我々は，まず，侵襲型アプリケータとして同軸スロットアンテナアレーを用いることとし，アンテナ周辺の温度分布について胸部ファントムを使用して測定した．さらに，specific absorption rate（SAR）分布を市販の電磁界シミュレーションソフトウェアを用いて計算した．これらの結果より，2本の同軸スロットアンテナを5 mm間隔で配置し，15 Wのマイクロ波電力を使用する同軸スロットアンテナアレーにて，腫瘍ファントム中の直径3 cm程度の領域の温度を42.5&deg;C以上に上昇させることができた．また，30分加温後の温度上昇値やSARは，正常組織のファントムよりも腫瘍組織のファントムの方がいずれも高い値になることがわかった．さらに，治療計画ソフトウェアを用いて小線源治療時の線量分布を検討すべく，乳房腫瘍患者の断層画像にシミュレーションを適用した．腫瘍サイズは50 mm（長さ）&times;50 mm（幅）&times;20 mm（厚さ）であった．6 Gyの放射線量を5回照射し，30 Gyの放射線量とした．この結果，同軸スロットアンテナアレーを用いて42.5&deg;C以上に温度上昇させる組織内加温法と，6 Gyを5回に分けて照射する小線源治療の併用は，深在性乳房腫瘤の局所制御を行える可能性があることがわかった．

<p>In this paper, a capacitive coupling Low Temperature Co-fired Ceramics (LTCC) chip antenna is designed and fabricated for Wideband Code Division Multiple Access (W-CDMA) mobile handsets applications. The proposed antenna is designed by utilizing the capacitive coupling structure and feeding by a microstrip line. The proposed antenna has the advantage of good gain and easy to impedance matching. The size of the proposed antenna is 3 × 10 × 0.94 mm³. Gain difference by microstrip-fed and CPW-fed is also discussed and comparative results are simulated and demonstrated. Measured results show that the impedance bandwidth for |S₁₁| less than −10 dB covers two bands of W-CDMA, and the omni-directional radiation pattern is realized.</p>

Along with the spread of novel types of mobile phones such as smartphones, there has been increasing public interest in the health hazards associated with exposure to electromagnetic waves from these devices. Therefore, we estimated the specific absorption rate (SAR) of electromagnetic radiation by numerical simulation using a realistic computational smartphone model with an antenna for a third generation communication (3G) system (operating frequencies: 900 MHz and 2 GHz) and computational human models with the anatomical structures of Japanese male and female adults. We also assessed the relative variability of SAR based on holding a smartphone at various positions for data communications. The 10-g-averaged SAR (SAR(10g)) when the smartphone was operating at 2 GHz was generally higher than that at 900 MHz independent of the placement of the smartphone. Moreover, we found that SAR(10g) had a tendency to increase when the smartphone was placed vertically in relation to the torso. In addition, it is possible that SAR(10g) variability depends mainly not on placement height but on tilt angle.

This paper describes the detection of tissue coagulation for a microwave surgical device. This method uses variations in the electrical properties of biological tissue before and after heating. To evaluate the proposed method, we made coagulated tissue and measured the impedance of the tissue using the microwave surgical device. The results of the measurements show that the impedance of the heated tissue changed significantly due to tissue coagulation. This results implies that coagulation of tissue can be detected by variation of electrical impedance.

Microwave coagulation therapy (MCT) is an effective treatment for hepatocellular carcinoma. During MCT, the target region is heated to induce coagulation in the tissue, including cancer cells. Several types of antennas for MCT have been developed, the heating performances of which were evaluated via specific absorption rate (SAR) and temperature distribution. However, for coagulation therapy, detailed evaluation of the coagulated region is important. Therefore, a newly developed algorithm is presented for calculating the coagulated region within biological tissue. To confirm the validity of the proposed method, the calculated result is compared with the experimental findings.

Until now, the 700 MHz band has been used for the field pickup unit (FPU), which is used for the live broadcasting of events, such as marathons and long-distance relay races. However, the frequency band is slated to migrate to 1.2 and 2.3 GHz bands based on an action plan for radio spectrum reallocation developed by the Ministry of Internal Affairs and Communications, Japan. With the frequency migration of the FPU, the size of transmitting antennas can be downsized. Therefore, 1.2 and 2.3 GHz band antennas can also be mounted on wireless cameras for professional-use. In this study, we measured the specific absorption rate (SAR) on the body of the operator exposed to electromagnetic waves radiated from the transmission antenna of the wireless camera via a 1.2 GHz band. We also calculated the SAR to confirm the validity of the measurement method, and we compared the measured results with the calculated ones. As the result, SAR distributions between the measured and the calculated results were nearly identical. It is thus possible to evaluate the SAR using the method suggested in this paper.

Variation of the dielectric properties of tissues could happen due to aging, moisture of the skin, muscle denervation, and variation of blood flow by temperature. Several studies used burst-modulated alternating stimulation to improve activation and comfort by reducing tissue impedance as a possible mechanism to generate muscle activation with less energy. The study of the effect of dielectric properties of biological tissues in nerve activation presents a fundamental problem, which is the difficulty of systematically changing the morphological factors and dielectric properties of the subjects under study. We tackle this problem by using a simulation and an experimental study. The experimental study is a novel method that combines a fat tissue-equivalent phantom, with known and adjustable dielectric properties, with the human thigh. In this way, the dispersion of the tissue under study could be modified to observe its effects systematically in muscle activation. We observed that, to generate a given amount of muscle or nerve activation under conditions of decreased impedance, the magnitude of the current needs to be increased while the magnitude of the voltage needs to be decreased.

© 2015 Elsevier Ltd. Variation of the dielectric properties of tissues could happen due to aging, moisture of the skin, muscle denervation, and variation of blood flow by temperature. Several studies used burst-modulated alternating stimulation to improve activation and comfort by reducing tissue impedance as a possible mechanism to generate muscle activation with less energy. The study of the effect of dielectric properties of biological tissues in nerve activation presents a fundamental problem, which is the difficulty of systematically changing the morphological factors and dielectric properties of the subjects under study. We tackle this problem by using a simulation and an experimental study. The experimental study is a novel method that combines a fat tissue-equivalent phantom, with known and adjustable dielectric properties, with the human thigh. In this way, the dispersion of the tissue under study could be modified to observe its effects systematically in muscle activation. We observed that, to generate a given amount of muscle or nerve activation under conditions of decreased impedance, the magnitude of the current needs to be increased while the magnitude of the voltage needs to be decreased.

Recently, wireless radio terminals such as mobile phones and tablet computers are increasing and developing rapidly. The effects of the electromagnetic (EM) waves in the human body from the wireless radio terminal have been paid attention. Therefore, we have calculated the specific absorption rate (SAR) in human tissues radiated from simple EM source models as like dipole antennas. In this paper, we constructed high-resolution numerical model of the flip phone and tablet computer. In addition, we compared the SARs in human body from the flip phone and the tablet computer using the finite-difference time-domain (FDTD) method. As the results, we found the SARs by the flip phone are higher than those by the tablet computer. All calculated SARs are below the safety guideline for RF energy exposure set up by the International Commission Non-Ionizing Radiation Protection (ICNIRP).

Body-centric wireless communications (BCWCs) have become an active area of research due to many applications such as health care system, identification system and entertainment. In this paper, a dual-mode antenna for body-centric wireless communications is studied. In on-body mode, the antenna is similar to a pair of metal electrodes operating at 10MHz and in off-body mode, with an L-shaped slit embedded, the antenna can cover the 2.45 GHz ISM band. Measured results, including received voltage at 10 MHz, reflection coefficient, radiation patterns and received power in the 2.45 GHz ISM band are presented to validate the proposed antenna. Since the proposed antenna is applied in BCWCs, we used two arm phantoms for 10 MHz and 2.45 GHz in measurement. © 2013 EurAAP.

RFID system is a growing technology for various applications such as logistics management and automatic object identification, and medicine management. In recent years, it is suggested to combine with in-body wireless communications to reduce medical error and improve quality of live (QOL) of patient. In this paper, we designed the tag antenna which integrates with an integrated circuit (IC) chip of 9.3 - j55.2 . The antenna is embedded into the three-layered human arm phantom and the performance is simulated by finite-difference time-domain (FDTD) method. In addition, by use of the handy reader, the maximum read range of 1.3 cm of the proposed antenna can be reached, that is approaching the theoretical value of 1.7 cm by the link budget. © 2013 Antenna Society of the Chinese Institute of Electronics.

Small implantable devices have been investigated with great interest for wireless medical applications because of the promise of different clinical usages in order to promote patient's independence. In these implanted device systems, the antenna plays an important role as a part of transmitting and receiving power. Therefore, the research on the antennas for implantable devices (implantable antennas) is important. In this study, we propose an implantable helical folded dipole antenna for short-range wireless communications. The antenna is designed to operate at 2.45 GHz, one of the industrial-scientific- medical (ISM) bands. We have analyzed some performances of the proposed antenna. The results show that the proposed antenna can be a candidate as an implantable antenna. © 2011 EurAAP.

Microwave coagulation therapy (MCT) has been employed mainly for treatment of small size tumors. In the treatment, thin microwave antenna is inserted into the tumor and microwave energy heats up the tumor up to at least 60°C for generation of enough coagulated volume including the target tumor. During the microwave radiation, reflection coefficient of treatment antenna changes significantly. In this paper, possibility of coagulation monitoring was found observing the reflection coefficient change of the antenna by numerical calculations and measurements. © Saito and Ito.

This paper provided a measurement campaign of simple antenna system mounted on a vehicle by utilising a Japanese geostationary test satellite called Engineering Test Satellite VIII (ETS-VIII). We developed an antenna system that was compact, light weight, and promising in low cost production. The antenna system was built by a 16-cm patch array antenna, which had simple satellite-tracking method that controlled by a control unit as the vehicle's bearing was updated from a navigation system in real time. A Global Positioning System (GPS) module was utilised for navigation system to provide accurate information of the vehicle's position and bearing during travelling. The control unit was used as the antenna-beam control and measured-data acquisition. The antenna system was thoroughly examined in the measurement under the line of sight (LOS) areas as well as the blockage areas in order to evaluate the propagation characteristics caused by utility poles, pedestrian overpasses and vegetation-covered road. In this measurement, received signal power and average bit error rate (BER) were simultaneously retrieved. Steadily received levels and BER were satisfactorily attained during satellite-tracking in LOS area. Moreover, the fade characteristics and BER performance were investigated while signal blockage happened. The measurement results were presented here to grasp their attenuations and effects on the bit error rate in terms of fade depth. With these results, we can consider to design a cost-effective mobile satellite application for future technology. © 2010 IEEE.

Hyperthermia is one of the modalities for cancer treatment, utilizing the difference of thermal sensitivity between tumor and normal tissue. The authors have developed a coaxial-slot antenna for microwave hyperthermia. In this paper, calculated results of temperature distributions around the coaxial-slot antenna for the treatment of brain tumor and bile duct carcinoma are described. © 2005 IEEE.

The microwave coagulation therapy(MCT)is one of the minimally invasive microwave thermal therapies and has been employed for the treatment of small size tumor. This paper describes the improvement of the antenna for the MCT.