A pressure sensor for measuring intradiscal pressure (IDP) has been developed. This sensor consists of a stainless steel needle (outside diameter, ∅1.2mm) which is provided with a semiconductor pressure sensor chip at the tip and a grip which contains a unique circuit to correct zero-point setting and sensitivity that would be affected by temperature change. In addition, this sensor makes it possible to measure IDP directly by the pressure sensor chip built in the lateral side of the tip, and to record the pressure-tropic property of the gel nucleus pulposus. Considering the data of clinical use in 18 patients, it is concluded that the newly developed intradiscal pressure sensor is sufficient to be used extensively in a clinical setting. And a difference between intradiscal vertical and horizontal pressure was observed. In addition, this sensor is used safely, accurately and easily with a percutaneous pressure measurement method.

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Recent neurophysiological experiments showed that neuronal dendrites could be recognized as active systems rather than passive transmission lines due to the existence of varied types of voltage-gated ionic channels. This study is performed to clarify functional significance of such an active propery of neuronal dendrites. In order to achieve this, a compartment neuron model is constructed so that the model closely mimicks the most recently found responsiveness of neurons with active dendrites. Based on the model, generation and propagation of action potentials and the associated behavior of intracellular Ca²⁺ concentration are simulated for various combinations of synaptic inputs. Inhibitory synaptic inputs are found to control the propagating dendritic area of the action potentials. Since the propagation of the action potential is accompanied by an increase of intracellular Ca²⁺ concentration, the inhibitory input could shape synaptic organizations on the dendritic tree through the well-known Ca²⁺-induced synaptic plastihity. In addition, an action potential generation in the soma is shown to differentiate levels of the interacellular Ca²⁺ concentration in the whole dendritic area. Finally, we reach the hypothesis that the activeness of the dendritic system could serve to broadcast the information concerning somatic firing to the whole dendritic tree, which is mediated by the associated increase of the intracellular Ca²⁺ concentration.

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We have developed a new heart rate monitoring system using a 24GHz microwave Doppler sensor by which heart rate can be measured over a clothed body without contact. This monitor estimates a slant of vector trajectory composed of two detected signals that are orthogonal to each other so as to improve the detectable sensitivity. Therefore the monitor can detect the heart rate which is independent of the change in range from sensor to body, and has a resolution about the displacement range 10μm. A moving average filter is used to reject respiratory signal that has large displacement and obstructs the heart rate to be detected clearly. Then the monitor can count on the heart rate with high sensitivity and stability. In this paper, we explain the principle of detection for displacement measurement, and show the performance of the monitor, the minimum detectable displacement and the examples of detection. The theoretical and experimental errors of the estimated slant are also shown.

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Recent advances on the digital electroencephalograph has allowed us to use different derivations of the recorded electroencephalogram (EEG). In this paper, a new method for quantitative interpretation of the posterior dominant rhythm in awake background EEG was developed using combined EEG derivations. Dominant rhythm is the most important phenomena in background EEG and gives information on fundamental brain activities. Both referential derivation and biporlar derivation of EEGs were slectively used for calculating the items of dominant rhythm interpretation. Furthermore fluctuations of the background EEG activities and the activation of ear-lobe reference electrode were considered. Those improvements have shown a good agreement with the visual inspection of the dominant rhythm for the data of 28 subjects. Differences of the interpretation way of respective electroencephalographer were also investigated. The proposed method can be employed as a part of the automatic EEG interpretation system previously proposed by the authors, and will broaden the range of the application.

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An accurate head model is required to get reliable solutions for the inverse problem in electroencephalograph. However, no practical method is available to measure tissue conductivities in a head, and hence the standard values are assumed for all the subjects so far. In this paper, we propose a kind of least square method to estimate the conductivities of scalp, skull and brain from potential distributions generated by weak currents injected from scalp surface, and verify its effectiveness by means of computer simulations using concentric sphere head models. The standard 4-shell concentric sphere model was used to calculate potential distributions that are considered as measured ones after being added with some noise. Then the conductivities were estimated from these potential distributions assuming 3-shell concentric sphere models with different thickness of the scalp and the skull. Errors in the estimation of dipole locations were also investigated using concentric sphere models with the conductivities thus obtained. As a result, we came to the following conclusions. (1) It is difficult to estimate the brain conductivity only from scalp potentials. However, it is not so crucial to know the precise value of the brain conductivity in the estimation of the scalp and skull conductivities as well as dipole locations. They can be estimated with practical accuracy by just assuming a rough value for the brain conductivity. (2) Errors in the thickness of the scalp and the skull reflect errors in their estimated conductivities. However, the conductivity of the scalp multiplied by its thickness and the conductivity of the skull divided by its thickness can be estimated accurately from scalp potentials. So long as these two parameters are given correctly, estimated dipoles are located near the true ones regardless of the errors in the thickness and conductivities of the scalp and the skull as well as the brain conductivity.

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The power of the high-frequency (HF) region in the power spectral density function of heart rate variability has been recognized as an indicator of parasympathetic nervous system activity and is expected to be applicable as an evaluation parameter not only for the autonomic nervous system but also for mental and physical workload. To quantify HF power in accordance with the power spectral density (PSD) estimated by Fast Fourier Transform (FFT) or autoregressive model, several kinds of different methods have been suggested. These methods, for example, calculation of the PSD area from 0.15Hz to 0.5Hz, calculation of the area of the specific band width around the HF component and that utilizing the peak value of the HF component, do not always yield the same result in the tendency of HF power. To evaluate the performance of these methods quantitatively, simulation data were induced and the “error rate” of each method was calculated and compared. The error rate showed that the method by which PSD was estimated by FFT and the HF power calculated by the area of specific band width around the HF component was robust against noise and was effective in measuring HF power in the spontaneous breathing condition.

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We assessed the breast tumors in magnetization transfer ratios (MTRs) and pathological findings. We measured MTRs of 52 breast tumors. The breast tumors included six cystic tumors, two malignant lymphomas, three mastopathies, two fibroadenomas, four phyllodes tumors, and 35 invasive ductal carcinomas. MTRs were calculated by using the equation 100×(M_off-M_on)/M_off, where M_off and M_on were the measured signal intensities on the conventional SPGR and MT-prepared SPGR images. There were statistically significant in MTRs between the tumors excepting the mastopathies and mammary glands. The MTRs of carcinoma were greater than those of benigh tumors. The richer in stromal compornent tumors had higher MTRs. The richer in cellular tumors had lower MTRs. The MTRs of tumors showed correlation with water structure in tumors. The MTRs may be a new and useful parameter for tissue characterization of the breast tumors.

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We describe a system of fluorescent X-ray computed tomography using synchrotron radiation (SR-FXCT) to image nonradioactive contrast materials. The system operates on the basis of computed tomography (CT) scanned by the pencil beam. In the previous experiment, we have imaged an acrylic cylindrical phantom with cross-shaped channel, filled with a diluted iodine-based tracer material of 200μg/ml. This research is aimed to improve image quality, to select the optimum energy of the incident X-ray, to confirm quantitative evaluation of the image, and to demonstrate FXCT image for living body. First, we simulated output energy profile by the Monte Carlo simulation and confirmed to predetermine the incident X-ray energy at 37keV, in order to separate the fluorescent photons from background scattering components. Next, the imaging experiment was performed by using conventional CT algorithm under the optimum parameter at the Tristan Accumulation Ring, KEK, Japan. An acrylic phantom containing five paraxial channels of 5 and 4mm in diameter, could be imaged; where each channel was respectively filled with diluted iodine-based contrast materials of 50, 100, 200 and 500μg/ml. From the reconstructed image, we confirmed quantitativity in the FXCT image. Finally, a rat's brain was imaged in vitro by FXCT and monochromatic transmission CT. The comparison between these results showed that the iodine-rich region in the FXCT image corresponded with that in the monochromatic transmission CT image.

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A new method is presented for reducing artifact caused by translational motion along phase-encoded direction in magnetic resonance imaging (MRI). The method using the wavelet analysis of magnetic resonance signals has advantages beyond earlier methods: (1) a standard spin-warp imaging sequence is used to postprocess magnetic resonance signals; (2) ghost artifacts can be reduced without blurring of the image; and (3) it is not necessary to know a priori information on the patient. The availability of the method is illustrated by a computer simulation and analysis of magnetic resonance signals obtained from a real MRI system.

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Restoration of motor function of the paralyzed patient by means of multichannel Functional Electrical Stimulation (FES) is effective as a medical treatment. In the clinical application of FES, many electrodes which we developed are implanted for selective control of individual muscles. Because of the low percentage of electrode failure in the body, stable FES control has been achieved for a long time. However, expanding the FES application causes the increase in the number of electrode failure even if the percentage of the failure is low. Therefore, a quantitative evaluation of implanted percutaneous electrodes for FES is required in clinical site. We developed a new measuring system of the electrode impedance over the frequency range of 20Hz to 10kHz. This measurement made it possible to estimate whether the implanted electrode is broken or moved. In addition, it could also provide information of disconnection status between the electrodes and the stimulator. The characteristics of the electrode impedance can easily discriminate the electrode condition, i. e., breakage, movement, etc., without surgical operation. This new evaluation method is quite useful in clinical site.

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We developed an intelligent infant incubator system, named the Hyper Incubator. Purpose of the Hyper Incubator system is to keep and reinforce the mutual relationship between the baby and his/her family, particularly the mother who is usually separated from her baby. The Hyper Incubator transmits various information regarding the baby in it and inner environment parameters by means of World Wide Web technology on the Internet. The developed system was also thought to be useful for the use by medical personnel residing on an intranet within the hospital information system.

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