Yoshio Nikawa

Soft and dry phantom modeling material using silicone rubber with carbon fiber

New phantom models that can simulate the effect of electromagnetic waves on human tissues have been developed. These phantom models can be designed to fit a wide range of complex permittivities by using two types of carbon fiber within a silicone rubber base. Tissues with low water content, such as fat and bone, and tissues with high water content, such as skin and muscle, can both be modeled using the phantom models discussed in this paper. When using conventional phantom model materials, care must be taken to prevent decomposition and dehydration during storage. The materials used for these new phantom models do not dry out and can be used repeatedly with reliable results.

Application of microwaves and millimeter waves for the characterization of teeth for dental diagnosis and treatment

This paper presents applications of microwaves and millimeter waves for the characterization of teeth. This is done by measuring the complex permittivity over the frequency range from 0.04 to 40 GHz. These measurements have revealed that dental caries are significantly more lossy to microwaves and millimeter waves than the healthy tooth, and this difference can be used for dental diagnosis. The experimental results have been confirmed by using the finite-difference time-domain (FDTD) method. In addition, millimeter-wave heating of the lossy dental caries can be used as a sterilization treatment. It is concluded that millimeter waves can be used for dental medical diagnosis as well as dental medical treatment.

Development and Testing of a 2450-MHz Lens Applicator for Localized Microwave Hyperthermia (Short Paper)

A new type of applicator with a convergent lens for localized microwave hyperthermia is developed. A lens applicator of direct contact type was designed to conduct actual and progressive experiments with phantoms of simulated fat and muscle tissues heated at 2450 MHz. The experimental results showed that the heating power penetration depth increased 40 percent with this applicator as compared to a simple rectangular waveguide applicator with the same size aperture that had generally been used for microwave hyperthermia. Our applicator had a concave-shaped aperture and was designed to contact well with the heating medium whose shape was cylindrical like a human body.

A Direct-Contact Microwave Lens Applicator with a Microcomputer-Controlled Heating System for Local Hyperthermia

A direct-contact lens applicator for local microwave hyperthermia is proposed and developed with a computer-controlled microwave heating system. The applicator is a practical one that can converge the radiated electromagnetic field to deposit its energy deep in human tissues. The experimental results, which agree well with the theoretical ones, show that the applicator which operated at 2450 MHz could heat at twice the depth at which a simple and conventional waveguide applicator could heat. The experimental results using a developed computer system that supplies microwave energy and circulated cooling water to the developed applicator show that the fluctuations of temperature at the heating location in the human tissue model were maintained within +-0.3° C of the set temperature. The results of the phantom model and the animal experiment using the system with the applicator show that the maximum depth of noninvasive heating was more than 30 mm below the surface. These results are available for the clinical hyperthermia treatment of cancer.

An Electric Field Converging Applicator with Heating Pattern Controller for Microwave Hyperthermia

A new type of applicator for microwave hyperthermia at 430 MHz has heen developed. The applicator, which consists of an integrated waveguide array, has a convergent effect of the radiated electromagnetic (EM) field in Iossy dielectric media, and it can change the heating pattern in the medium with ease. The electric field distributions from the aperture of the applicator were measured in a saline solution having a concentration of 0.2--0.6 percent which served as the model of simulated human tissues. The results show that when using the above applicator, the location of maximum intensity of the electric field conld be generated inside of the dissipative medium. The calculations of temperature distribution were performed in the model by using the experimental results of the electric field distribution. The applicator could change the transverse electric field distribution inside the medium, and then could control the depth of tissues located to the hyperthermic range. The heating range available for hyperthermia rising our single applicator is maximum 60 mm in depth theoretically.

Study on dental diagnosis and treatment using millimeter waves

In order to diagnose dental caries noninvasively, the transmission coefficient of the dental caries is measured and compared to that of a sound tooth. It has been revealed that dental caries are significantly more lossy than a sound tooth in millimeter waves. This characteristic can be utilized as a new caries diagnosis method. This paper also presents microwave and millimeter-wave heating results for the lossy dental caries that can be used as a sterilization treatment. Temperature-distribution results from microwave power heating have revealed that dental caries are easily heated. Furthermore, the results of the calculated specific absorption rate distribution using the finite-difference time-domain method indicate the possibility of caries treatment by millimeter-wave heating. It is concluded that millimeter waves can be used for dental medical diagnosis and treatment.

Dielectric-loaded lens applicator for microwave hyperthermia

The authors describe a lens applicator which can concentrate the E-plane field in a lossy medium and is constructed of an easily fabricated, dielectric-filled waveguide. Since the microwave field distribution on the aperture can be varied by using different sizes of dielectric material, the heating pattern inside the medium can be changed, allowing the configuration of a compact applicator that can heat portions deeper within the human body. Heating experiments on a model simulating human muscle have shown that an applicator with an aperture of 150*100 mm/sup 2/ achieves a maximum heating depth of over 80 mm, results that are compatible with the deep, localized heating required by hyperthermia. >

Blood-Sugar Monitoring by Reflection of Millimeter Wave

Diabetes mellitus has now emerged as a serious public health problem in Asia. To control blood glucose level, blood-sugar monitoring is necessary. Nevertheless non-invasive blood-sugar monitoring technique has not been in practical use. Complex permittivity of blood is very sensitive to the glucose concentration in microwaves. In this paper, a new technique is proposed to obtain blood glucose level using a resonant applicator non-invasively. It is found from in vivo measurement of reflection coefficient using the resonant applicator, blood glucose level can be obtained by measuring the value of reflection coefficient at the resonant frequency.

Application of millimeter waves to measure blood sugar level

Measurement of blood sugar level by non-invasive method is desirable. Nevertheless, a practical non-invasive technique has not been reported. In this paper, to measure blood sugar level using millimeter wave non-invasively, complex permittivity of glucose mixed sodium chloride solution is measured and the change of transmission coefficient in millimeter wave region obtained. An applicator system to measure blood sugar level in vivo is designed and optimized by simulation using Transmission Line Modeling (TLM) method.

Non-invasive measurement of blood sugar level by millimeter waves

Measurement of blood sugar level by noninvasive method is highly desirable. Nevertheless, a practical non-invasive technique has not been reported. In this paper, to measure blood sugar level using millimeter wave noninvasively, complex permittivity of glucose and sodium chloride solution is measured and the change of transmission coefficient in millimeter wave region is obtained. An applicator system to measure blood sugar level in vivo is designed and optimized by simulation using transmission line modeling (TLM) method.