Michio Miyakawa

Image restoration in chirp-pulse microwave CT (CP-MCT)

Chirp-pulse microwave computed tomography (CP-MCT) is a technique for imaging the distribution of temperature variations inside biological tissues. Even if resolution and contrast are adequate to this purpose, a further improvement of image quality is desirable. In this paper, we discuss the blur of CP-MCT images and we propose a method for estimating the corresponding point spread function (PSF). To this purpose we use both a measured and a computed projection of a cylindrical phantom. We find a good agreement between the two cases. Finally the estimated PSF is used for deconvolving data corresponding to various kinds of cylindrical phantoms. We use an iterative nonlinear deconvolution method which assures nonnegative solutions and we demonstrate the improvement of image quality which can be obtained in such a way.

The evaluation of skin friction using africtional feel analyzer

Background/aims: Sensory evaluation is an important factor for cosmetic products. Several devices for the measurement of sensory properties have been developed in recent years. The objective here is to measure skin surface friction using these devices and examine the correlation with other physiological parameters in order to evaluate the potential of physical measurement of tactile sensation.

Development of EOG-Based Communication System Controlled by Eight-Directional Eye Movements

A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift. Eight directional cursor movements and one selected operation were realized by logically combining the two detected channel signals based on threshold setting specific to the individuals. As experimental results using a projected screen keyboard, processing speed was improved to 12.1 letters/min. while the accuracy was 90.4%

A numerical study on the measurement region of an open-ended coaxial probe used for complex permittivity measurement

The measurement region of an open-ended coaxial probe with circular flange, which is used for measuring the complex permittivity, has been investigated by calculations and measurements. First, the detectable distance between the probe surface and metal plate in the saline solution is clarified by the experiments. Then, the electromagnetic field near the end of the probe, which affects the measurement strongly, has been analyzed by the finite-difference time-domain (FDTD) method. By identifying the measured and calculated results, the measurement region has been determined.

Experimental validation of a linear model for data reduction in chirp-pulse microwave CT

Chirp-pulse microwave computerized tomography (CP-MCT) is an imaging modality developed at the Department of Biocybernetics, University of Niigata (Niigata, Japan), which intends to reduce the microwave-tomography problem to an X-ray-like situation. We have recently shown that data acquisition in CP-MCT can be described in terms of a linear model derived from scattering theory. In this paper, we validate this model by showing that the theoretically computed response function is in good agreement with the one obtained from a regularized multiple deconvolution of three data sets measured with the prototype of CP-MCT. Furthermore, the reliability of the model as far as image restoration in concerned, is tested in the case of space-invariant conditions by considering the reconstruction of simple on-axis cylindrical phantoms.

In vivo assessment of pigmentary and vascular compartments changes in UVA exposed skin by reflectance-mode confocal microscopy.

Abstract:  Exposure of the skin to ultraviolet A (UVA) results in various biological responses, skin‐colour changes being among the major ones. Although intense research has been performed on UVA‐induced pigmentation and vascular changes, the process of skin‐colour changes after UVA irradiation remains unclear. For a better understanding of the UVA tanning mechanism, we here performed a human study in 27 healthy volunteers with skin phototype (SPT) II to VI. After a single UVA exposure to inner forearm, the skin sites were imaged using reflectance‐mode confocal microscopy (RCM), for analysis of melanin and vascular changes. Punch biopsies were also taken from the UVA‐exposed or non‐exposed sites for histological examination. Skin sections were stained with Fontana‐Masson and evaluated by a sensitive tyrosinase assay for comparison with RCM images. Furthermore, the effect of blood flow on skin‐colour changes was evaluated visually after administration of an intradermal anesthesia of lidocaine with or without epinephrine. Our RCM analysis showed dendritic melanocytes and a different melanin distribution in the epidermal layer, clearly visible 1 week after the UVA exposure in subjects of SPT V which were supported by histological examination. However, no melanin distribution pattern changes were apparent immediately after the exposure, while RCM images showed accelerated capillary flow patterns. The restriction of this UVA induced‐accelerated blood flow by epinephrine inhibited partially or completely the immediate pigment darkening and delayed tanning. These in vivo studies confirmed that vascular change is an important factor for the development of the immediate pigment darkening and delayed tanning.

Analysis of a hyperthermic treatment using a reentrant resonant cavity applicator for a heterogeneous model with blood flow

Hyperthermic treatment using a reentrant resonant cavity applicator is investigated. By solving time-dependent electromagnetic field-heat transfer equations for a heterogeneous model, temperature distributions in various organs are obtained. Calculated results show that it is indispensable to consider the blood flow to predict accurate temperature distributions during a hyperthermic treatment. Also, it is found that the necessity of measuring the electrical and thermal properties of the abdominal fat accurately as well as optimizing the heating system to avoid the concentration of electromagnetic energy around the abdominal fat-muscle interface.

Analysis of a hyperthermic treatment in a reentrant resonant cavity applicator by solving time-dependent electromagnetic-heat transfer equations

Investigates the analysis of a hyperthermic treatment. The time dependent electromagnetic-heat transfer equations are solved step-by-step considering the temperature dependencies of relative permittivity /spl epsiv//sub r/ and electric conductivity /spl sigma/. Close agreement between the calculated and measured temperature distributions is obtained. A technique to direct the electromagnetic energy toward a specific part of a homogeneous torso model is also noted.

Model-based permittivity measurement of construction materials by the standing wave method

A simplified model of a permittivity measurement system based on the standing wave method in free space has been developed to estimate the complex permittivity of construction materials accurately. It is assumed that the standing wave distribution is determined by three spherical wave components in this model that are the incident-, reflected- and scattered-waves at the edge of the material under test. The model is described by an equation in which the standing wave distribution is represented by the sum of those three wave components. By applying the least squares method to the model equation, the amplitudes and phase angles of those three wave components are estimated from the experimentally observed standing wave distribution. One can estimate the material permittivity from those estimated parameters of the model with high accuracy.

Control mechanism of an autonomous jaw-movement simulator, JSN/1C, during open-close movement

In order to clarify the control mechanism of jaw movements, the authors developed a robotized jaw simulator, JSN/1C, equipped with cable-tendon DC-servo actuators simulating masseter, lateral-pterygoid and digastric muscles. This simulator also incorporated a life-like compliance-control mechanism of the actuators, employing data of bite-force, tooth contact, cable-tension and cable-length. This updated mechanism enables the simulator to perform more natural open-close movements.