Session 1P4
Biomedical Applications of Electromagnetic Waves
Planar Applications for Local Thermotherapy
J. Vrba (Czech Technical University in Prague, Czech Republic); T. Drizdal (Czech Technical University
in Prague, Czech Republic); P. Togni (Czech Technical University in Prague, Czech Republic); R. Zajı́ček
(Czech Technical University in Prague, Czech Republic); L. Vı́šek (Czech Technical University in Prague,
Czech Republic); K. Novotná (Czech Technical University in Prague, Czech Republic); J. Vedralova
(Czech Technical University in Prague, Czech Republic); L. Pergl (Czech Technical University in Prague,
Czech Republic); L. Oppl (Czech Technical University in Prague, Czech Republic); . . . . . . . . . . . . . . . . . . .
Shorted Microstrip Applicators for Local Hyperthermia
T. Drizdal (Czech Technical University in Prague, Czech Republic); Paolo Togni (Czech Technical
University in Prague, Czech Republic); Megela Alexandr (Czech Technical University in Prague, Czech
Republic); Jan Vrba (Czech Technical University in Prague, Czech Republic); . . . . . . . . . . . . . . . . . . . . . . . .
Evaluation on Heating Performances of Antennas for Interstitial Thermal Therapies by Use of Tissueequivalent Solid Phantom with Capillary Blood Flow
Kazuyuki Saito (Chiba University, Japan); Atsushi Hiroe (Chiba University, Japan); Satoru Kikuchi
(Chiba University, Japan); Masaharu Takahashi (Chiba University, Japan); Koichi Ito (Chiba University, Japan); . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Implementation of Active Antennas in Medical Microwave Radio-thermometry
Svein Jacobsen (University of Tromsø, Norway); Ø. Klemetsen (University of Tromsø, Norway); . . .
Implanted Antenna for an Artificial Cardiac Pacemaker System
Tamotsu Houzen (Chiba University, Japan); Masaharu Takahashi (Chiba University, Japan);
Koichi Ito (Chiba University, Japan); . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Measurements of Dielectric Properties of Biological Tissues in Mm-wave Band by Free-space Reflection
Method, Ellipsometry Method and Coaxial Probe Method
Taiji Sakai (National Institute of Information and Communications, Japan); M. Hanazawa (National
Institute of Information and Communications, Japan); H. Wakatsuchi (National Institute of Information
and Communications, Japan); S. Watanabe (National Institute of Information and Communications
Technology, Japan); A. Nishikata (Tokyo Institute of Technology,, Japan); Osamu Hashimoto (Aoyama
Gakuin University, Japan); . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Effects of Parameters of a Dosimetric Human Model on Temperature Elevation Due to Millimeter-wave
Exposure
Akio Kanezaki (Chuo University, Japan); Taiji Sakai (National Institute of Information and Communications, Japan); S. Watanabe (National Institute of Information and Communications Technology,
Japan); Hiroshi Shirai (Chuo University, Japan); . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Induced Current Density in Adults and Children Exposed to Homogeneous Magnetic Field in Intermediate
Frequency Band
Kei Maruyama (Aoyama Gakuin University, Japan); Y. Suzuki (Tokyo Metropolitan University, Japan);
K. Wake (National Institute of Information and Communications Technology, Japan); Taiji Sakai (National Institute of Information and Communications, Japan); S. Watanabe (National Institute of Information and Communications Technology, Japan); M. Taki (Tokyo Metropolitan University, Japan);
Osamu Hashimoto (Aoyama Gakuin University, Japan); . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
39
40
41
42
43
44
45
46
47
40
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
Planar Applications for Local Thermotherapy
J. Vrba, T. Drizdal, P. Togni, R. Zajı́ček, L. Vı́šek, K. Novotná, J. Vedralova
L. Pergl, and L. Oppl
Department of Electromagnetic Field, Faculty of Electrical Engineering
Czech Technical University in Prague
Technická 2, 166 27 Prague 6, Czech Republic
Abstract—
Introduction: During last years we work on theory and applications of various types of applicators for microwave thermotherapy. In this paper we would like to describe some of our results for
planar applicators. Here mentioned examples of applicators are designed for working frequency
either 434 or 2450 MHz and optimized by aid of 3D electromagnetic field simulator SEMCAD.
Impedance matching measurements were done by aid of vector analyzer and SAR distributions
were evaluated using infrared camera.
Methods: All discussed applicators are developed on the 1,5 mm thick dielectric substrate with
relative permittivity εr = 4, 2. Two centimetre thick water bolus (εr = 78) is inserted between
the irradiating part of the planar applicator and agar phantom (σ = 0, 8 S/m, εr = 54). The
dimensions of the applicators were analytically calculated with respect to the working frequency
434 resp. 2459 MHz and then optimized by aid of 3D electromagnetic field simulator SEMCAD.
First example of these applicator is circular microstrip resonator which is placed on the square
substrate with dimensions 78 × 78 mm. The active part is composed of circular patch with radius
of 19 mm. The position of the feeding point is 17 mm from the center of the circular patch.
Next applicator is the circular slot-line resonator which is developed on the square substrate with
dimensions 80 × 80 mm. In this case the radius of the circular patch (active part) is 17 mm. The
width of the slot-line (7.5 mm for both applicators) gives the correct impedance matching for the
working frequency. The rest of the metallization which surrounds the slot lines forms the ground
planes. The last one is the rectangle microstrip line applicator with the dimensions 95 × 55 mm of
the substrate. The circumference of the microstrip line, which is equal to wavelength together with
3 mm width of the microstrip line provides good impedance matching at the working frequency.
Figure 1: Model of circular microstrip, circular slot-line and rectangle microstrip line applicator.
Conclusion: Different planar applicators were designed and evaluated. As an example three
selected applicators were described here, in our presentation we would like to give more informations on impedance matching and 3D SAR distribution of each of these applicators.
ACKNOWLEDGMENT
This research is supported by Czech Research Program: “Transdisciplinary Research in the Area
of Biomedical Engineering II” (MSM6840770012) and by Grant Agency of the Czech Republic
project: Medical Applications of Microwaves: “Therapy and Diagnostics” (102/05/0959).
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
Shorted Microstrip Applicators for Local Hyperthermia
Tomas Drizdal, Paolo Togni, Megela Alexandr, and Jan Vrba
Department of Electromagnetic Field, Czech Technical University in Prague
Technická 2, 166 27 Prague 6, Czech Republic
Abstract— Hyperthermia is a type of cancer treatment in which body tissue is exposed to
temperatures up to 45 C, in order to damage and kill cancer cells, or to make cancer cells more
sensitive to the effects of radiation and certain anticancer drugs. Local hyperthermia is used to
heat small areas which are mainly placed at the surface of the body. As we can quite simply
localize these tumours, thus the area which must be heated is clearly defined. The type of the
applicators selected for treatment depends on their radiated EM field patterns which give different
thermal distribution in the treatment area (our task is uniformly the tumour and minimize the
temperature enhancement in the healthy tissue).
This paper describes a circular microstrip (CMSA) and rectangular microstrip (RMSA) applicators for local hyperthermia which are designed for a working frequency of 434 MHz. Applicators
are developed on a 78 mm square dielectric board with a metallization on both sides. This board
(substrate) has permittivity εr = 4.1 and thickness of 1.5 mm. To reduce the geometrical dimensions of both applicators the patch is shorted to the ground plane in one point of the patch. The
designed geometrical dimensions as well as the position of feeding point were optimized using a
3D electromagnetic field simulator. The active part is in the first case composed of a circular
patch with radius of 19 mm and in the second case of a 36 mm square patch. The distance of
feeding point from the center is 17 mm for CMSA and is 16 mm for RSMA. Using these modifications the Shorted CMSA and RSMA were developed. An agar phantom (εr = 54, σ = 0.8 S/m)
was used as a model of biological tissue during the simulations. To protect the surface of the
agar phantom a two centimeters thick water bolus (εr = 78) is inserted between applicator and
agar phantom.
Impedance matching was measured using a network analyzer and 3D SAR distribution was
obtained using IR-camera and the results shows that this type of applicators can be used for
local hyperthermia.
41
42
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
Evaluation on Heating Performances of Antennas for Interstitial
Thermal Therapies by Use of Tissue-equivalent Solid Phantom
with Capillary Blood Flow
Kazuyuki Saito1 , Atsushi Hiroe2 , Satoru Kikuchi2 , Masaharu Takahashi1 , and Koichi Ito3
1
Research Center for Frontier Medical Engineering, Chiba University, Japan
2
Graduate School of Science and Technology, Chiba University, Japan
3
Faclty of Engineering, Chiba University, Japan
Abstract— In recent years, various types of medical applications of microwave have been extensively investigated and developed. In particular, the minimally invasive microwave thermal
therapies using thin applicators are of great interest. Until now, the authors have been studying
the heating performances of coaxial-slot antenna, which is one of the thin microwave antennas
for interstitial thermal therapies. In order to estimate the heating performances of the antenna,
numerical simulations and experiments by use of tissue-equivalent solid phantoms are performed.
It is possible to calculate the SAR (specific absorption rate [W/kg]) and the temperature distributions around the antenna inside biological tissue by the numerical calculations. However, in
the experiments, although the SAR can be estimated, measurement of temperature rise around
the antenna is difficult, because it is not easy to realize a tissue-equivalent solid phantom with
cooling effect by blood flow. Until now, the authors developed the tissue-equivalent solid phantom with a thick blood vessel and estimated the temperature rise by the coaxial- slot antenna. In
this study, the tissue-equivalent solid phantom with capillary blood flow was developed and the
temperature rise around the coaxial-slot antenna inside this developed phantom was experimentally measured. As a result of measurement, good agreement was observed between the measured
and the calculated temperature rise under some assumptions.
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
Implementation of Active Antennas in Medical Microwave
Radio-thermometry
S. Jacobsen and Ø. Klemetsen
Department of Physics and Technology, University of Tromsø, Tromsø, Norway
Abstract— Microwave radiometry is a spectral measurement technique for resolving blackbody radiation of heated matter above absolute zero. The emission levels vary with frequency
and medical radio-thermometers are short range instruments that can provide temperature distributions in subcutaneous biological tissues when operated in the microwave region. However,
a crucial limitation of the microwave radiometric observation principle is the extremely weak
signal level of the thermal noise emitted by the lossy material (−174 dBm/Hz at normal body
temperature). Requirements of long integration time (∼3–5 secs) and wide integration bandwidth
(∼300–50,MHz) result in a maximum of 5–6 radiometric bands per antenna within the usable
frequency scan range from 1 to 4 GHz.
To improve the radiometer signal-to-noise ratio, we propose to integrate a tiny, moderate gain,
low noise amplifier (LNA) close to the antenna terminals as to obtain increased detectability of
thermal gradients within the volume under investigation. The concept is verified experimentally
in a lossy phantom medium by scanning the active antenna across a thermostatically controlled
water phantom with a hot object embedded at d = 38 mm depth. The temperature gradient
between the target and environment was only 0.9◦ C. Analysis shows a marked increase in signalto-clutter ratio of the brightness temperature spatial scan profile when comparing active antenna
operation with a conventional passive setup.
43
44
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
Implanted Antenna for an Artificial Cardiac Pacemaker System
Tamotsu Houzen1 , Masaharu Takahashi2 , and Koichi Ito3
1
2
Graduate school of Science and Technology, Chiba University, Japan
Research Center for Frontier Medical Engineering, Chiba University, Japan
3
Graduate School of Engineering, Chiba University, Japan
Abstract— Recently, medical implant telemetry system (MITS) monitoring medical information such as a cardiac beat has been investigated with a great interest. A wireless telemetry
system which can transmit medical information without a wire piercing the skin has advantage
to prevent the infection with a germ in a medical diagnosis. An antenna embedded into the
human body which can be transmitted vital signals of a patient to the external equipment is fundamentally necessary for the realization of this system. In this paper, a planar inverted-F antenna
(PIFA) on the surface of an artificial cardiac pacemaker as an implanted antenna is proposed. For
the design of the antenna, the human body is substituted by the 2/3 muscle-equivalent phantom
and the analysis by finite-differential time domain (FDTD) method is used. The communication
link budget is additionally calculated for the estimation of the antenna in a real environment. As
a result, it is confirmed that the proposed antenna operating at 400 MHz-band can build up the
communication link of MITS with the external equipment which is located within 6 m distance
and 58 deg. altitude.
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
45
Measurements of Dielectric Properties of Biological Tissues in
Mm-wave Band by Free-space Reflection Method, Ellipsometry
Method and Coaxial Probe Method
T. Sakai1 , M. Hanazawa1 , H. Wakatsuchi1,2 , S. Watanabe1 , A. Nishikata3 , and O. Hashimoto2
1
National Institute of Information and Communications Technology, Japan
2
Aoyama Gakuin University, Japan
3
Tokyo Institute of Technology, Japan
Abstract— Permittivity of tissues is required to calculated electromagnetic dosimetry and it
is well known that permittivity has frequency dispersion. Therefore a number of measurement
methods of dielectric constant have been studied at many frequency bands. However, to our
knowledge, permittivity of tissues have not been reported in 20 GHz or more. There have been
strongly demands for a dielectric constant of tissues at millimeters wave band. In this study we
applied three methods to permittivity measurement of tissue in millimeter wave band.
There are many tissues that are difficult to obtain in large amount and to be cut in precisely
required shape for measurement. Open-ended coaxial prove methods have advantages with respect to these points. We employed the coaxial probe kit (Agilent 85070E 200 MHz–50 GHz) to
measure, because permittivity of tissues can be obtained even small volume i.e., 1 cm3 or without
cutting the tissues. Variations of measurement results are caused by several factors for example hardness of a sample, evaporation on the surface of a sample, pressing power of the probe
against a sample etcetera. In actual measurement it is difficult to realize these factors. Therefore
measurement results should be compared with other method’s results for reliability.
We developed two free-space measurement systems for permittivity of biological tissues. One is
reflection method and the other is ellipsometry method.
The reflection method measured a complex reflection coefficient from a flat sample at 18–50 GHz
using focus lens antenna. Measured reflection coefficients contain an effect of optical flat glass
which is set on the sample as cover of the holder. To remove the effect, S-parameter of cover
glass was also measured and was translated to T -parameter. And permittivity is estimated from
the reflection coefficient without the effect of glass.
The ellipsometry method is based on measurement of electromagnetic scalar value and observes
ellipsoidal polarized reflection wave which is caused by linear polarization wave exposure to a
sample. In millimeter wave measurement system, a horn antenna works as a polarized analyzer,
we can choose the “rotating antenna method” which corresponds to the rotating analyzer method
in optical region.
To confirm the validity of three methods, measurement results of water were compared with each
others at room temperature. And these data have a good agreement with each other although
the results of free-space methods have ripple.
46
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
Effects of Parameters of a Dosimetric Human Model on
Temperature Elevation Due to Millimeter-wave Exposure
A. Kanezaki1,2 , T. Sakai2 , S. Watanabe2 , and H. Shirai1
1
2
Chuo University, Japan
National Institute of Information and Communications Technology, Japan
Abstract— In recent year, expectations for millimeter-wave (30 GHz–300 GHz) technology are
rising with significant progress on information society. Because the exposure to millimeterwave will increase, it is important to evaluate the safety of millimeter-wave exposure. Most of
millimeter-wave power is absorbed within the surface of a human body and the absorbed power
causes temperature elevation in the body. Safety guidelines for millimeter-wave exposure are
based on warmth sensation and ocular effects. Especially, the warmth sensation is the fundamental basis of the safety guidelines in millimeter-wave band although details of characteristics
of the threshold of the warmth sensation has not been investigated. As one of basic analyses, we
investigated effects of parameters of a dosimetric human model on temperature elevation due to
millimeter-wave exposure using a threelayers model that consists of skin, fat and muscle.
Transmission-line theory was used to analyze the specific absorption rate (SAR [W/kg]) distribution in the human-body model. The temperature distribution in the human-body model
exposed to millimeter-wave has been calculated with bioheat equations [1]. We applied a constant temperature at the boundary in the deep region of the layer model and a heat transfer at
the boundary between the skin surface and air as described in [2]. The difference forms were
numerically calculated with an implicit method which accelerates the difference calculation [3].
We investigated effects of thickness of each layer of the human model and skin water content on
temperature elevation due to millimeter-wave exposure. The dielectric properties of biological
tissue were set for the degree of the water content as described in [4].
We found higher temperature elevation when skin thickness decreases and fat thickness increases.
We also found that the temperature elevation increases with decreasing skin water content. In
this study we investigated the effects of the physical parameters of the human model, i.e., the
width and water content of the tissues, on the temperature elevation due to the millimeter-wave
exposure. Our study is useful to establish the worst case of the human model to investigate
the safety of the millimeter-wave exposure although further investigations, e.g., the effects of
physiological parameters such as blood flow and the effects at other frequencies, are necessary.
REFERENCES
1. Hoque, M. and O. P. Gandhi, “Temperature distribution in the human leg for VLF-VHF
exposures at the ANSI recommended safety levels,” IEEE Trans. Biomed. Eng., Vol. 35, No. 6,
442–449, 1988.
2. Bernardi, P., M. Cavagnaro, S. Pisa, and E. Piuzzi, “Specific absorption rate and temperature
elevation in a subject exposed in the far-field of radio-frequency sources operating in the 10–
900-MHz range,” IEEE Trans. Biomed. Eng., Vol. 50, No. 3, 295–304, 2003.
3. Patankar, S. V., Numerical Heat Transfer and Fluid Flow, Hemisphere Publishing Corporation,
New York, 1980.
4. Wang, J., O. Fujiwara, and S. Watanabe, “Approximation of aging effect on dosimetric tissue
properties for SAR assessment of mobile telephones,” IEEE Trans. Electromagn. Compat.,
Vol. 48, No. 2, 408–413, 2006.
Progress In Electromagnetics Research Symposium 2007, Prague, Czech Republic, August 27-30
47
Induced Current Density in Adults and Children Exposed to
Homogeneous Magnetic Field in Intermediate Frequency Band
K. Maruyama1,3 , Y. Suzuki2 , K. Wake3 , T. Sakai3 , S. Watanabe3 , M. Taki2 , and O. Hashimoto1
1
Aoyama Gakuin University, Japan
Tokyo Metropolitan University, Japan
3
National Institute of Information and Communications Technology, Japan
2
Abstract— Currently, electrical appliances like IH hob have been used in various places. Therefore, public concern have been rising for the possibility of biological effect caused by magnetic
field due to such a electrical appliances. IH hob uses time varying magnetic field around 20 kHz
for fundamental heating frequency. In ICNIRP guideline [1], magnetic field strength with intermediate frequency is limited by induced current density to protect nerve system. A lot of
analyses have been done [2, 3] to investigate the relationship between the strength of incident
magnetic field and induced current inside of human body. There are a few studies to compare
current densities between adult and child induced by intermediate frequency magnetic field. The
purpose of this study is to clear the differences of induced current density distribution for the
realistic numerical models with wide range of age group.
We applied the impedance method [4] to calculate current density induced by uniform magnetic
field within adult male and children models for various ages. In this calculation, we use four
numerical human models, which are adult male, 3, 5, and 7 years old, respectively. The adult
male was developed based on MR images [5]. The child models were built on the adult male
model by reduction and deformation. Each model has 51 tissues and spatial resolutions are
2 mm. Calculation conditions are as follows. The strength of magnetic flux density is 1 µT.
The frequency is 20 kHz. Three types of incident magnetic field are employed to investigate
dependence of current density distribution on the direction. The directions of magnetic field
are from front to back, right to left and top to bottom against to human models. Results
of current density distribution are averaged over a cross-section of 1 cm2 perpendicular to the
current direction. The maximum values of averaged current density are compared for each model
and each incident direction. The maximum values of current density also compared within central
nerve system.
As a result, maximum value of current density obtained by child models do not exceeded that
value for the adult male model. Maximum values inside of nerve organizations were much lower
than the maximum value within trunk and head.
REFERENCES
1. International Commission on Non-Ionizing Radiation Protection, “Guidelines for limiting exposure to time-varying electric, magnetic, and electoromagnetic fields (up to 300 GHz),” Health
Phys., Vol. 74, 494–522, 1998.
2. Dimbylow, P. J., “Induced current densities from low-frequency magnetic fields in a 2 mm
resolution, anatomically realistic model of the body,” Phys. Med. Biol., Vol. 43, 221–230,
1998.
3. Xi, W., et al., “Induced electric currents in models of man and rodents from 60 Hz magnetic
fields,” IEEE Trans. Biomed. Eng., Vol. 41, 1018–1023, 1994.
4. Orcutt, N. and O. P. Gandhi, “A 3-D impedance method to calculate power deposition in
bioloical bodies subjected to time vaying magnetic fields,” IEEE Trans. Biomed. Eng., Vol. 35,
577–583, 1988.
5. Nagaoka, T., et al., “Development of realistic high-resolution whole-body voxel models of
Japanese adult males and females of average height and weight, and application of models
to radio-frequency electromagnetic-field dosimetry,” Physicsin Medicine and Biology, Vol. 49,
1–15, 2004.