Toshifumi Sugiura

Feasibility of using the automatic generating system for quartz watches as a leadless pacemaker power source

An automatic power-generating system (AGS) which converts kinetic energy into electric energy for quartz watches was tested as a power source for implantable cardiac pacemakers. An automatic power-generating mechanism and a capacitor (0.33 F) were removed from a quartz watch (SEIKO) and encapsulated in a polyvinyl case. Characteristics of the AGS were investigated by acceleration equipment. The capacitor in the AGS was charged to 2.0 V (0.66 J) by placing it on the equipment for about 30 minutes. The equipment has a 2 Hz cycle and generates ±1.7 G at the end of each half cycle. The AGS (fully charged to 2.0 V) was used as the power source for a pulse generator circuit built using commercially available CMOS IC. The circuit generated pulses of 0.5 ms width at 1 Hz (60 pulses min−1). The voltage of the AGS was maintained at 1.6 V while it was being charged by the accelerations. The generator supplied pulses of 0.75V, 1.47 mA through a 510Ω load. With fully charged AGS, the generator was also used to pace a mongrel dogs heart at 140 beats min−1 for 60 minutes. During pacing, the AGS supplied 420 mJ to the circuit and the cardiac muscle. The AGS was placed on the right ventricular wall of the mongrel dog under anaesthesia. Energy of 80 mJ is stored in a capacitor by the heart beating at about 200 beats/min for 30 minutes. Thus the AGS generated 13 μJ per heart beat. This result suggests that the AGS may supply enough energy for use in a cardiac pacemaker.

Retrieval of Temperature-Depth Profiles in Biological Objects from Multi-Frequency Microwave Radiometric Data

A method of retrieving a temperature-depth profile in biological object from a set of multi-frequency microwave radiometric data has been developed. The method is a combination of model-fitting and Monte Carlo techniques and is capable of estimating a profile and its confidence interval as a function of the depth. We use 2σ -intervals as a measure of the precision of tissue temperature measurements. The method was tested and supported by an experiment in which temperature distributions in a muscle equivalent agar phantom were measured using a 5-band, 1-3.8 GHz radiometer with the brightness temperature resolution of 0.05-0.07 K. A typical result of the experiment showed that 2σ -intervals were 1 K or less for 0 < z < 3 cm, 1.4 K at z = 4 cm, and 3 K at z = 5 cm. A numerical simulation study was made using this technique to assess effects of the selection of measurement frequencies, number of frequency bands, brightness temperature resolution of radiometer and thickness of fat layer on the precision. Resul...

A fuzzy approach to the rate control in an artificial cardiac pacemaker regulated by respiratory rate and temperature: A preliminary report

Fuzzy theory was applied to the rate control of a cardiac pacemaker which uses two parameters, respiratory rate and temperature, as the parameters for rate regulation. Using 25 fuzzy reasoning rules derived from five mongrel dogs, the pacing rates in three animals were calculated and compared with the intrinsic heart rates. It is concluded that the fuzzy method is well suited for the rate determination of a multi-parameter rate-responsive cardiac pacemaker.

A Three-Band Microwave Radiometer System for Noninvasive Measurement of the Temperature at Various Depths

An experimental three-band (1.5,2.5,3.5+-0.5GHz) radiometer system and a data analysis procedure have been developed for noninvasive measurement of the temperature at various depths in a biological body. Using them, we made temperature measurement experiments on the abdominal region of rabbits. The results of the experiments demonstrate the feasibility of the multifrequency radiometry for this purpose.

Low temperature phase diagram of In-Ga-P ternary system

Abstract The In—Ga—P ternary phase diagram in the low temperature region, 600–800°C, in the In-rich corner has been experimentally obtained and calculated based on the quasi-regular model with the assumption of a non-ideal solid. The liquidus lines were determined at 600, 650, 700, 750 and 800°C by weight loss method. The solidus compositions were measured on the epitaxial layers grown by the temperature difference method. Fairly good agreement between the data and calculated results was obtained.

Automatic discrimination of arrhythmia waveforms using fuzzy logic

A method was proposed for discrimination of ventricular arrhythmias using fuzzy logic. The classifier uses four features of ECG waveforms; amplitude variation ratio, interval variation ratio, peak sharpness, QRS complex width, and assigns each waveform a number of 0-100. The performance of the algorithm was evaluated on the surface and intracardiac electrocardiograms of ventricular tachycardia (VT), ventricular fibrillation (VF) and normal sinus rhythm (NSR) in mongrel dogs. NSRs were evaluated 90-100 while VFs less than 10. VTs were assigned the numbers of 30-75. An automatic detection and defibrillation experiment was performed with this algorithm.

A method of solution for a class of inverse problems involving measurement errors and its application to medical microwave radiometry

Retrieval of temperature-vs.-depth profiles in a biological tissue structure from multifrequency microwave radiometric measurement data constitutes a typical inverse problem in which the data involve relatively large measurement errors. The authors have developed a method of solution for a class of problems of this type. The method gives solutions in terms of the confidence interval and level. It also has a built-in capability of assessing the degree of fit of solutions to unknown actual source distributions. An agar phantom experiment and computer simulation based on a five-band (1-4-GHz) radiometry were performed to test the method, and the results are presented.<<ETX>>

Wearable ECG Recorder with Acceleration Sensors for Monitoring Daily Stress

A small and light-weight wearable electrocardiograph (ECG) equipment with three accelerometers (x, y and zaxis) was developed for prolonged monitoring of autonomic nervous system in daily life. It consists of an amplifier, a bandpass filter, a microcomputer with an AD converter, a triaxial accelerometer, and a memory card. Four parameters can be sampled at 1 kHz (10 bits) for more than 24 hours, maximum 27 hours, with a default battery and a memory card (1 GB). The availability of the system was tested for three subjects for three days by replacing the battery and the memory card every 24 hours under each environment. Both short-term and circadian rhythms of the autonomic nervous system were clearly observed. The change of the autonomic nervous system from body movement (i.e. walking or turning over) was observed by check acceleration data. The feasibility of the application in clinical practice is also discussed.

Cardiac pacemaker regulated by respiratory rate and blood temperature.

A new method using respiratory rate and temperature as the guides for optimal pacing is proposed. A pacemaker was fabricated which senses these two parameters simultaneously. The pacemaker functions by calculating the cardiac rate, which would he derived from the respiratory rate and the blood temperature. The higher of the two rates is adopted as the cardiac pacing rate, i.e., at which stimuli will be delivered. The operation was tested in a mongrel dog with complete atrioventricular block. After the induction of anesthesia, a thermistor temperature probe was inserted into right atrium and a respiratory rate sensor was attached around the chest. After administration of a pyrogenic drug, both respiratory rate and blood temperature increased. The pacing rate was increased from 178 beats/minute(bpm) at 36.4°C. blood temperature, and 26.5 acts/minute(apm), respiratory rate, to 233 bpm at 40.1°C and 40.0 apm. Cardiac output was increased from 2.25 liters/minute(1/pm) at the beginning to 2.50 l/pm at maximum. The transition of the guide from respiratory rate to temperature was observed at about 38°C.

Wearable ECG recorder with acceleration sensors for monitoring daily stress: Office work simulation study

A small and light-weight wearable electrocardiograph (ECG) equipment with a tri-axis accelerometer (x, y and z-axis) was developed for prolonged monitoring of everyday stress. It consists of an amplifier, a microcomputer with an AD converter, a triaxial accelerometer, and a memory card. Four parameters can be sampled at 1 kHz for more than 24 h and a maximum of 27 h with a default battery and a memory card of one giga byte (1 GB). Off-line data processing includes motion information along three axes and autonomic nervous system (ANS) activity bispectral analysis and the tone-entropy method (T-E method) from HRV data. The availability of the system was tested through simulated office work and three-day monitoring by replacing the battery and the memory card every 24 h. Both short-term and circadian rhythms of ANS activity were clearly observed. In addition, sympathetic nervous activities gradually increased from the second to the third day. The experimental data presented verifies the functionality of the proposed system.