A basic study on the accuracy of fetal heart rate measurement has been performed experimentally using a signal generator as the FHR generator. It was found that a measurement error of 3.5ms or less was necessary to conclude that the existence of variability at the fetal heart beat rates of around 140bpm was a reality and that it was not false variation caused by noise. The measurement accuracy of the cardiotocomonitor used in these experiments was 0.78ms when measuring fetal heart beat rates of 140bpm.
Meanwhile, the following equation holds between the lowest value for STV (short-term variability) which can be measured accurately and the measurement error (in this case, the STV index is the one proposed by Heilbron).
STV=0.159σ_ε, STV=√1-ρ/2σ; that is, ρ, represents the correlation coefficient between T_i and T_i+1, while σ represents the standard deviation of T_i.
It can be concluded that a measurement accuracy of 0.156ms is required to measure STY of 1ms accurately. Inversely, STV of 5 ms is the lowest value which can be measured with an accuracy of 0.78ms. A higher measurement accuracy will be needed to clarify the ambiguous clinical significance of STV.

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Despite frequent use of dental casts in the measurement of shapes of teeth and palate in daily practice, only a few reports on three-dimensional measurement of a dental cast are available. We have developed a computer-controlled device for the optical profile measurement of a dental cast using a laser and an image-sensor. A focused laser beam scans the dental cast which is fixed on a X-Y table. During the scanning the vertical positional change of the light spot on the cast is detected with a uni-dimensional 2048-pixel image-sensor. The device has been designed to achieve data aquisition time of 25 msec per point, measurable depth range of 40mm and minimum scanning pitch of 0.1mm. Experimental results show that longitudinal and lateral resolutions are within 0.05 and 0.1mm, respectively. As for the image processing, an algorithm of edge detection of the occlusal surface for the purpose of displaying a dental arch is described. The paper also refers to three-dimensional movement of the teeth during orthodontic treatment which is calculated by way of superposition of three-dimensional data taken from casts before and after the treatment.

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This paper is concerned with a role of the central nervous system in the predictive motor control function. To evaluate such a human operator's function effectively, his compensation characteristics for time delay in the compensatory manual control system with a random step input have been obtained. The effect of two central nervous system diseases, Parkinsonism and cerebellar ataxia, on the predictive control function is discussed through operators' frequency responses, coherency functions, and so on. Futhermore, the hypothesis that the human predictive control behavior is produced by means of the process model in the motor coordination system is examined in comparison with data obtained from the patient and normal subject groups.
The following results have been obtained.
(1) Patients with Parkinsonism or cerebellar ataxia have functional disorders of predictive control.
(2) The closed-loop systems controlled by patients with cerebellar ataxia have a relatively wide bandwidth but they are fairly oscillatory and have the nonlinearity similar to the systems controlled by patients with Parkinsonism.
(3) An impediment in the predictive control function of the patient with cerebellar ataxia may be caused by the malfunction of the process model in the cerebellar cortex to predict the future state of the neuro-muscular system or the controlled object.

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It is of little practical value to make estimation of electric cardiac activities, which have clinical importance, in a straightforward way on the basis of the body surface potential because of possible noise. This difficulty can be overcome by utilizing more information about physiological functions and structure of the heart as well as of the torso. As the first step, a 3-dimensional heart model has been constructed, and initiation and propagation of action potentials in it were simulated: The result was in good agreement with Durrer's observations. As the next step, a 3-dimensional torso, which includes the present cardiac model, has been formed and the body surface potential was calculated by means of the boundary element method. The computing time for generating each potential map, including propagation of action potentials, is 15 sec. Values of the parameters in the present model are subject to easy alterations so that calculations may match the observations.

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It has not been confirmed whether Holter ECG is adequate for ST segment analysis. The present paper presents a report on the characteristics of a Holter ECG (Del Mar Avionics 445 A/666 A/667 B) such as 1) the transmission characteristics measured with a new method (white noise response) in addition to those with the conventional methods (sinusoidal and rectangular wave responses), 2) the system noise spectra and 3) reproducibility of ECG waveform. By using the white noise response method proposed, a detailed continuous amplitude response can be obtained within a short measuring time. The amplitude response of Holter ECG ranges from 0.07 to 30Hz (-3dB). It sharply decreases as f^-4.5 above 30Hz and has some undulations of about 7dB due to the contour effect below 1Hz. The reproduced ECG waveforms are accompanied with some reductions in the amplitudes of R waves, disappearance of Q waves, and noticeable distortion in ST segment.
It is shown that the frequency characteristics of Holier ECG system under test does not satisfy AHA standards. In conclusion, Holter ECG tested here is not yet ideal for ST segment analysis.

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A new method of biotelemetry is proposed, which realizes nonrestrained acquisition of biological signals using the infrared light diffused out from animal skin. This technique is fundamentally different from conventional telemetry techniques which use radio-frequency electromagnetic waves.
An optical transmitter which consists of some LED's is implanted beneath the skin. Biological information such as ECG signal is collected in vivo and the light emitted from the LED's is modulated by the signal. The light transmitted through the skin is strongly diffused and spread out in a wide angle. The light is collected by the remotely located optical receivers and the biological information is obtained by demodulating the signal. Thus, the biological information in vivo is obtained without restraining the object with cables or optical fibers.
In order to verify the possibility of the above technique, a system, which obtains an ECG from laboratory animals, has been developed. An infrared light was chosen due to its invisibility and high transmittance through the skin. Considering the stability of the communication link and the power consumption of the implanted transmitter, PFM (Pulse Frequency Modulation) technique was used. Using the system, the transcutaneous ECG telemetry was performed successfully.
In the experiment, the indirect light reflected and scattered by the walls, the ceiling and the floor was shown to be useful in the optical telemetry. Light transmission patterns through the skin of a mouse were measured. The results suggest the possibility of telemetry even from the deep part of the body cavity.
It is concluded that recent progress of optical and electronic technologies have reached the point, where transcutaneous optical telemetry of biological signals has become practically possible.

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