An automated processing technique to extract the LV contour from RI-angiocardiogram and to, compute the LV volume is proposed. An original fuzzy image is first transformed into well defined image by the nonlinear enhancement technique and LV contour is then determined by employing both thresholding and differentiation on this enhanced image. By thresholding at the density level determined from the enhanced image's histogram, a two-value figure indicating a composite region of left ventricle and left atrium is obtained, and the anterior-inferior part of the LV contour is obtained from this figure. Then, the boundary separating the left ventricle and left atrium, which becomes the posterior part of the LV contour, is detected by horizontal spatial differentiation. These two parts of the contour extracted separately are combined into the complete LV contour. The apex and the aortic valve line are located on the LV contour by using the curvature information of the LV contour, and LV volume is computed by the Simpson's integral method.

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This paper describes an end-user oriented data base system POD (Patient Oriented Data Base for Medical Research) which has been developed to provide the most convenient tool for medical research activities. By means of end-user languages, DDL, STORE and QUERY, a researcher physician can easily define his data base, maintain it and use the data in it himself for his research purposes.
The DDL is a data definition language to define the data structure of the data base by means of filling out a Data Definition Table. The STORE is a language to generate the data base and to update it, which includes four commands : CREATE, ADD, DELETE and UPDATE. The QUERY is a query language to retrieve the data stored in the data base and to analyze the basic statistics of the data, which includes eight commands : DEFINE, SELECT, SORT, LIST, HISTOGRAM, TABLE, MEAN and DTEST which were carefully chosen and designed on the basis of several years of experience at the University of Tokyo Hospital. The QUERY is designed to meet about 95 percent of physicians' requirements for statistical analysis. More complicated calculations can be achieved using a FORTRAN interface.
The basic data structure of a patient's record consists of two levels of hierarchy : an ID-record, a higher level record, including non-chronological data of the patient and DATA-records, lower level records, including chronological data. Each record has a bit-pattern to compress blank elements, which results in a remarkable reduction of the file volume without any complication of the data structure or increase of the processing time.
The processing system is written in FORTRAN language for machine independence, so that the system can run on most computers with little modification.

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Metal microelectrodes used in physiological studies exhibit large noise due to their high impedance. In this paper we present measured noise spectra over the frequency range of 0.05 Hz to 1 kHz for platinum, tungsten, and stainless steel microelectrodes.
The noise of metal microelectrodes shows a f^-0.2 to f^-2.3 frequency dependence when measured in 0.9% NaCl solution. By comparing the measured noise with thermal noise as given by Nyquist theorem from the resistive part of electrode impedance, the following properties are understood.
In the high frequency range (f >1-100 Hz) thermal noise dominates at rest potential and also under the condition of direct current application (less than a few 100, μA/cm²). At low frequencies, electrode noise exceeds thermal noise even at rest potential. Usually, the ratio of power spectrum density of measured noise to that of thermal noise for W electrodes at 10 Hz falls in the 10 to 100 range. W electrodes show the largest ratios followed by Pt and stainless steel electrodes. The ratios tend to increase with unit area polarization resistance.
When direct current passes through the Pt electrode, the low frequency noise greatly increases. Particularly, at about 10, uA/cm² anodic current a large noise peak is observed. For extremely small tip microelectrodes, this current density is often caused by a leak current of usual J-FET input amplifier.
The measurement resolution of bioelectric signals is determined by electrode noise, since noise of metal microelectrodes having impedance above several 100 kΩ at 100 Hz is comparable to or larger than J-FET input amplifier noise.

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We have solved the gas transport equation for the model built from a modified form of Weibel's anatomical data to describe the airway geometry. The equation treats simultaneous convective flow and longitudinal diffusion and incorporates uneven distribution of ventilation.
The slope of the alveolar plateau results in the main from regional inhomogeneity caused by the asynchronous ventilation in the airways. The stratified inhomogeneity is concurrently present as the secondary effects of regional inhomogeneity.
The model was also used to explain the paradoxical phenomena of nitrogen washout tests in the patients with fibrosis, that is, the slope of the alveolar plateau of the single-breath washout test is steep in spite of the single exponential clearance curve of the multi-breath washout test on the same subject. The analysis of the solution of our equation leads us to the conclusion that : this phenomenon is caused by the following pulmonary characteristics of fibrosis : 1) the regional inhomogeneity throughout the distal airways, 2) the decrease of the regions in which diffusion plays a main role of gas transport, 3) the increased contribution of convective flow and 4) the increased relative common dead space to regional inhomogeneity.

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A computer simulation model of the spread of excitation in the ventricle is described.The heart is constructed in the memory unit of the computer in the form of a model with the human ventricle replaced by blocks closely packed in hexagonal lattice. The individual blocks correspond to the regions of each cardiac muscle cells and the properties of those blocks are derived fromanatomical physiological properties. The simulated spread pattern shows high fidelity coincidence with observations in animal experiment. The boundary region of spread in excitable cells shows electric field. The electriclfiield forms the electrocardiogram. The electrocardiogram is also constructed mathematically on the basis of Wilson's double layer theory. Constructed QRS-T wavepatterns demonstrate the characteristic patterns in clinical electrocardiogram.

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Transfer characteristics of mechanoreceptors in the frog's sartorius muscle to stretching were analyzed as multi-channel transducers working in the peripheral nervous system with the following methods.
(1) Two pairs of metal bipolar electrodes (Pt and Ag-AgCl) were used for recording afferent impulse trains of two separate channels having different amplitudes.
(2) A computer system (OKITAC-4300C) with a high-speed A/D converter and a disk memory (2.5 MW) was used to analyze waveforms of nerve impulses and to calculate characterizing parameters of the waveforms.
(3) These parameters were the absolute values in the rising and the falling phases of impulse waveforms, respectively, and the time intervals thereof.
(4) The two-dimensional amplitude histograms with these parameters were reconstructed in order to separate several receptor units having similar impulse waveforms from a series of nerve impulse discharges. The main clue to the reconstruction is the synchronization of impulses in both series of impulse trains.
The experimental results revealed that the mechanoreceptor systems were composed of several different receptor units of different transfer gains (impulse frequency/displacement) and of different activation thresholds for mechanical stretches.

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This paper describes a new biomedical electrode, the surface of which is coated with oxide film for sensing various, biomedical potentials. Although metallic electrodes and pipette electrodes are employed in general as biomedical sensing electrodes, a number of disadvantages are seen in their use. For example, biomedical signals are distorted by the use of metallic electrodes due to drift noise generated by the electrochemical reaction between metal and electrolyte.
In order to minimize the effects of drift noise, research has been conducted in which a dielectric silicon oxide film was introduced between electrolyte and electrode. This silicon oxide film is deposited on an aluminum plate by means of vacuum process using silicon monoxide powder. The dielectric film can be produced accurately even on metallic electrodes as small as a needle.
The biomedical electrode using silicon oxide film in the manner described above has the following advantages :
1) The DC balancing potential as well as polarization potential do not appear rin the amplifier input.
2) Since the electrode does not require an electrolytic paste, it is suitable for long-term monitoring.
3) It is chemically stable and will not corrode.
4) It is free, of any, piezo effect.
5) With this electrode, the patient is protected from electric shock caused by DC current.

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The compliance values of the thoracic aorta were measured by the simultaneous recording of the transthoracic electrical admittance plethysmogram and the intra-aortic pressure in four dogs. Preliminarily, the compliance values measured by this method were compared with those obtained from the pressure-volume relationships in three different silicon tubes. These two groups of values were almost equal to each other.
The mean compliance value in the normal animals was C= (6.26±1.47 (SD)) ×10^-5 cm⁵/dyn; the mean aortic pressure and heart rate during the data collection were 84-145 mmHg (109±23.4) and 122-187 per minute (154 ±20.4), respectively. In attempting to compare these data with other previously reported data, the compliance (C) was converted into that of the elastic modulus (E= (2.77±0.805) × 10⁶ dyn/cm²). The velocity (v) of the pulse-wave determined from this value with Moens-Korteweg equation was v=4.77±2.46 m/s.

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The effects of using the head support on visual evoked potential (VEP) have been investigated experimentally. Monochromatic flashes (green) of 50 msec duration were presented to the right eye of the subject at the rate of 1.6 Hz. Active electrodes were placed on the inion, and on the position 8 cm above the inion along midline of the head, and a reference electrode was placed on the mastoid bone behind the right ear. Then VEP's were recorded in bipolar and monopolar configurations using the telemetry unit. As a result, amplitudes and latencies of bipolar and monopolar VEP's were altered markedly by the use of the head support with a good long-term and intersubjective reliability. The alterations of the waveform were quite different from the results reported by Bickford et al., which were contaminated with myogenic responses, and from the results reported by Ebe et al., which were influenced by the background EEG pattern. Our results indicate that this phenomenon is not explained by the above previous findings.

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Clinical manifestations of water, and salt deficiencies of the body are considered to reflect decrease of intracellular and extracellular fluid space respectively. They are often expressed interchangeably in so many different synonyms.
However, more rigorous quantitative analysis of the whole body water and salt deficit vs. volume changes in the body fluid compartments would be required for any diagnostic scheme of precise determination of the losses as a guide line to fluid therapy to be established.
We have derived the relationship between intra- and extra-cellular fluid space based on the biophysical properties of cell membranes. This relationship is presented in various diagrams. For instance, on a chart of orthogonal axes of water and salt content of the body, on which the families of equi-intracellular and equi-extracellular volume curves are drawn, body fluid balance, physiological reactions, and course of fluid therapy can be expressed as vectors.
These expressions would prevent us from using ambiguous terminology such as dehydration.

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Bayes' theorem and multivariate analyses have been used to simulate the process of medical diagnoses. However, in these studies some mathematical models had to be assumed, which are not necessarily related to the real process of physicians' diagnoses. Because of this fact, the results of these studies Were sometimes difficult to evaluate.
Physicians usually make decisions according to some rules which were obtained in their, long experiences. If there are some methods which can simulate the same process as physicians, the methods will be more acceptable in the field of medical decision making by computers. “MYCIN” developed by Shortliffe and others demonstrated this possibility by using the methods of artificial intelligence techniques. On the basis of similar considerations, we have developed a program named “MECS-AI” (Medical Consultation and Education System by Artificial Intelligence) which makes diagnoses and suggests treatments in cardiovascular diseases.
In this study rules which physicians use for the diagnosis and treatments were collected. The rules were organized in the form of premises and actions. When some data of a patient are given to the system, the system searches the premises of the rules and find the ones to apply to take proper actions. Then with this tentative conclusion, it continues to search for the next rules until it reaches some conclusions. The program is written in LISP language.
This system is now being evaluated by cardiologists of the University of Tokyo Hospital. It seems that this system has wide area of applications in physicians' consultation and medical education.

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