Jin-ichi Matsuda

A re-entrant type resonant cavity applicator for deep-seated hyperthermia treatment

A heating method using a re-entrant-type resonant cavity applicator for deep-seated hyperthermia treatment and its computer simulation are described. In this heating method, a human body is placed in the inner gap of the cavity and is heated by standing-wave electromagnetic fields. From the results of computer simulations using a disk phantom, it is shown that a deep and local tumor may be heated effectively without generating any hot spots or edge effects as in the case of an RF capacitive heating method.<<ETX>>

Three-dimensional reconstruction of magnetic stray fields using reflection electron beam tomography

In this paper, a method of reconstructing three-dimensional magnetic stray fields on the surface of a magnetic recording head using reflection electron beam tomography is presented. An algorithm for reconstructing the magnetic flux density in three dimensions from the deflection vectors of the electron beams has been developed and tested. An application to a one-turn coil model, which is used as the simplest model of a magnetic head, is presented.

Hyperthermia applicator based on a reentrant cavity for localized head and neck tumors

A new applicator based on a reentrant cavity is proposed for treating localized tumors such as those of the head and neck. In order to effectively heat the localized tumor without causing dissipation of heat into the surrounding normal tissues, the electric field must be localized over the target region. Although a small applicator may produce an appropriate localized electric field, the higher resonant frequency due to downsizing of the equipment results in very poor heating distribution; this occurs due to the changes in electric permittivity and conductivity consequent upon an increase in the resonant frequency. In this article, we introduce a method for reducing the resonant frequency by inserting a dielectric material into the applicator; the efficacy of this method has been determined by calculating the electromagnetic field and heating distribution with the help of the finite element method. By using the proposed applicator, a reduction in the resonant frequency and localized heating over spherical regions 100 mm in diameter can be achieved.

Improvement of the resonant cavity applicator for brain tumor hyperthermia

A re-entrant type resonant cavity applicator for deep tumor hyperthermia treatment was presented. In this method, a human body is placed between the gap of the inner re-entrant cylinders, and is heated with electromagnetic fields stimulated in the cavity without contact between the surface of the human body and the applicator. First, a comparison of the heating characteristics of our heating method and RF capacitive heating method was discussed experimentally. At the position of half-length of phantom radius, the normalized temperature values using our heating method and RF capacitive heating method on the r-direction are 0.75 and 1.0, respectively. At the center of the phantom, the normalized values on the z-direction are 1.0 and 0.45, respectively. Second, the clinical heating results of the dog brain using our heating method were presented. In the experiment, the deep region of the dog brain is heated to 42.5C From these results, it is confirmed experimentally that deep regional heating can be done noninvasively without generating hot spots under the surface area of the brain.A re-entrant type resonant cavity applicator for deep tumor hyperthermia treatment was presented. In this method, a human body is placed between the gap of the inner re-entrant cylinders, and is heated with electromagnetic fields stimulated in the cavity without contact between the surface of the human body and the applicator. In this paper, two methods to control the heating pattern were proposed. In the first method, a human body was moved towards the electrode. In the second method, the diametric ratio of the inner electrode was changed. The controllable range of heating pattern was about 20% of the distance from the center of the agar phantom in the direction of depth

TV‐rate histogram equalization processor for the electron microscope

A fast (NTSC TV‐rate), low cost, simple histogram equalization processor is described. In this apparatus, the histogram equalization processing is carried out by the table look‐up method at TV‐rate. The characteristics of the processor, and its applications to the real time and on‐line processing of weak contrast images from the Ultra‐High Voltage Electron Microscope (Osaka University) are described. With this apparatus, equilevel processing, level compression, and level slicing may also be easily carried out.

A study on bioelectrical impedance analysis (BIA) for measuring the amount of visceral fat by numerical simulation

A newly bioelectrical impedance analysis (BIA) method for measuring the amount of visceral fat volume in a human body, which is an important index for diagnosis of the metabolic syndrome, is proposed, and its possibility is discussed numerically. The conventional BIA method has been known as an inexpensive and non-invasive one, but its measurement accuracy is not reliable due to the influence of the subcutaneous fat volume surrounding the visceral fat volume in the human body. To overcome this problem, we prepare a new electrode arrangement consisting of two pairs of electrodes and use two modal current flows between these electrodes to remove the influence of the subcutaneous fat volume. According to our numerical simulation using the simplified phantom model of a human body by the finite difference method (FDM), it is expected that the amount of visceral fat volume can be evaluated approximately in high accuracy by our new method.

Computer processing for quantitative medical thermography

A periodic variation of the skin surface temperature on the order of one cycle per second with a magnitude of 0.1 degrees C affects the accuracy of quantitative infrared thermography. A recently developed computer-assisted synchronous thermographic system is described that allows detailed and more essential information on the dynamics of physiological functions to be obtained from a time series of thermograms without any effects due to temperature variation. Computer simulation reveals that this surface-temperature variation corresponds to the pulsatile change of blood flow through arterioles in the dermis.<<ETX>>

Generation of electron beams by low–temperature field emission

A method is proposed of generating a fine electron beam which has an excellent monochromaticity and high brightness by using an extremely low temperature and high electric field. This paper describes the actual apparatus based on the proposal. If the cathode of the apparatus is kept at an extremely low temperature (about 4K), theoretically, the possibility exists of making the energy spread as small as of the order of 0.01 eV, while the energy spread of a conventional electron beam at room temperature with a high electric field is of the order of 0.1 eV. The prototype apparatus assembled consists of a 3-electrode type electron emission system, the main part containing a retarding potential energy analyzer and a vacuum chamber (about 10−9 Torr) made of stainless steel. Polycrystal tungsten wire is used for the cathode. The reduction of the energy spread was not achieved for the theoretical value, because of the deposits on the tip surface due to the residual gas (notably oxygen) at the extremely low temperature (cooled by liquid helium). At a low temperature (cooled by liquid nitrogen), however, the energy spread was improved by 25% compared with that at room temperature. This shows a possible improvement of the energy spread by cooling the cathod as expected.