Iyo denshi to seitai kogaku. Japanese journal of medical electronics and biological engineering最新文献

A local impedance and its change were measured using a tetrapolar circuit combined with magnetic eddy current generator. By this method, current distribution can be restricted to a desired part, so as to eliminate errors due to uncertainty of the resistance between the electrode and the skin. The resistivity of a substance in a biological model measured by this method was nearly equal to that of the substance separated from the model. Sensitivity and localization were assessed in the other model composed of a piece of metal plate in a saline pool. The detection sensitivity was validated theoretically. The localization of the impedance pulsatile waveforms, measured at the proximal part of the forearm, was consistent with that of the arteries at this part. These results suggest that this method using eddy current should expand the application area of bio-impedance measurements.

Laser beams have been in common use for the treatment of hyperpigmented skin lesions. However, therapeutic efficacy has been limited mainly because the output is circular with a Gaussian distribution of intensity, which makes it difficult to apply a uniformly distributed dose to the lesions. We have developed a technique whereby a laser beam is converted to have a square and uniform output intensity distribution. The principle of this technique is that the divergent laser beam enters a glass square pillar, propagates through the pillar repeating the total reflection and emerges with a uniform intensity distribution over the cross-section at the end of the pillar. The device applied this technique is incorporated in a hand-piece and both ruby and argon laser systems have been developed. The ruby laser has been used for the treatment of the melanistic skin lesions such as nevus cell nevus and nevus spilus. In clinical application, 36 of 67 cases have shown remarkably effective results with an improvement rate of 53.7%. The argon laser has been used for the treatment of vasogenic skin lesions such as portwine stain. In clinical application, 44 of 66 cases have shown effective results and the improvement rate is 66.7%. These results are excellent when compared with the other methods of treatment and with laser therapy previously used.

Microcomputer-based anesthesia delivery system using mass flow control devices has been developed. System is superior in computer control to conventional anesthesia machine because there is no mechanical setting. System consists of three thermal mass flow controllers (TMFC), one vapor source controller (VSC), personal computer system, and air circuits. Personal computer system has facilities of digital output, analogue input and analogue output interfaces. TMFCs and VSC are devices which operational principle is based on the thermal conductance and they are controlled by electrical signals from computer in the system. TMFCs control the mass flow of nitrous oxide, oxygen and carbon oxide according to each input voltage signal. VSC regulates mass vapor of halothane in order to keep set value up by means of alteration of oxygen carrier gas flow. Computer always monitors the gas flow of the TMFCs and VSC so that computer compensates the change of the carrier gas flow of VSC by regulating the TMFC for oxygen. Mixed gas from TMFCs and VSC is supplied through the air circuit to subject. Characteristics of the system was measured by mass spectrometer and flowmeter. Stability was 0.05% change after 30 minutes at the initial set of 3%. Experiment on animals using mongrel dogs has been performed to verify the system functions.

We developed control system of total artificial heart (TAH) during exercise simulating the circulatory response of natural heart. The following procedures were taken to develop this system. 1) Measurement of hemodynamics and physical activity rate (PAR) of natural heart goats during treadmill exercise. 2) Estimation of cardiac output from PAR using a non-linear model. 3) Development of a pneumatic artificial heart (AH) driver with high speed controllability and a control unit to deliver CO calculated from PAR beat by beat. 4) Evaluation of the physiological condition of the TAH goat during exercise controlled by this system. Using this control method, CO of TAH goats was similar to that of natural heart goats during treadmill exercise. Hypertension was observed during exercise. This hypertension was considered to be derived from two causes. One was high inflow and outflow resistance of cannulae between AH pump and living body. The other was the disorder of peripheral circulatory control mechanism in TAH animal. Such as increased sympathetic activity, insufficient secretion of atrial natriuretic polypeptide (ANP) and decreased sensitivity of peripheral circulatory system with ANP.

An on-line digital simulator using microcomputer system was developed to mimic the hemodynamic behavior of the human circulatory system under ventricular assist device (VAD) pumping. This simulator could calculate the response to the variation of the cardiac function or the driving mode of VAD in the real-time fashion. This simulator was used as the mock controlled object to evaluate and improve the algorithm of an adaptive controller of the drive unit for VAD. The adaptive one-step ahead controller was introduced as the precompensator for the PI-controller, which decides the outflow volume from VAD in order to follow up the reference flow value by changing the systolic duration. It was confirmed that the proposed adaptive control system improved the response speed of the VAD driving system automatically according to the variation of the controlled object.

A new passive telemeter for the intracranial pressure monitoring have been developed. The completely implantable pressure sensor used in this system consists of a crystal, a coil and a ferrite rod attached on a diaphragm. The pressure on the diaphragm alters the volume of air in the receptacle and then the ferrite rod moves in and out of the coil and alters the resonance frequency of the sensor. Although the sensor doesn't have a battery or other energy storer, for example, a capacitor, the resonance frequency can be measured without contact. Therefore, at any time, we can measure the intracranial pressure with this sensor implanted under the scalp beforehand. However, not only pressure but also temperature alters the resonance frequency of the sensor, because the volume of air alters in proportion to temperature. Hence, we have developed a new passive telemetry pressure sensor which contains a passive telemetry temperature sensor. The temperature sensor consists of a coil and a special crystal whose resonance frequency varies with ambient temperature and its resonance frequency can be measured in the same way that we measure the resonance frequency of pressure sensor from outside of the body. With this system, we can measure the intracranial pressure about 60 times per second and the intracranial temperature every 8 seconds. The measured value of the pressure was automatically corrected by analog temperature correcting electric circuits. In animal experiment, the output of this system was similar to one of the catheter-tip type pressure transducer and we could observe the intracranial pressure altered synchronizing with respiration and with heart beat.