Purpose of this article is to review the recent developements in digital techniques for radioisotope imaging (R. I. imaging). Firstly, various types of R. I. imaging devices are briefly introduced and a special emphasis placed on rectilinear scanner and Anger camera in connection with subsequent data processing. Then, methods of digital data acquisition from the scanner and the camera are surveyed from to literature and an on-line data processing system for the imaging devices which will be commissioned at National Inst. of Radiological Sciences this year is described in detail. Brief explanations of software are made for on-line data acquisition from the scanner and the camera which will be employed in our system. These data-acquisition systems store the data in the form of an array of counts in small areas that is called a “digital image”.
Since one of the purposes of the digital R. I. imaging is to obtain more intelligible pattern for diagnosis than that in conventional imaging, several processing have been performed on the “digital image” in order to reduce the noise to deteriorate the R. I. image. In this work, smoothing, restoration and differential imaging are applied to the image of thyroid phantom obtained by a rectilinear scanner.
Finally, the methods of displaying these image data by computer-controlled C. R. T., X-Y plotter and line printer are described.
Another purpose of the digital imaging is to obtain quantitative information that is characterized by the image pattern itself. It opens a way to the pattern recognition and automatic diagnosis. Future work in this direction is briefly discussed.
Although digital R. I. imaging is now under rapid developement, it is hoped that this will produce useful information for nuclear medical diagnosis which was unable to extract in the past.

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In the field of dental clinic the radio telemetering technique provides a new fruitful method to study the stomatognathic system and has several advantages to observe physiologically the system of unrestrained subject.
The transmitter available now can send solely such the discrete information as that expressed by on and off of a switch. Though some possibilities of transmitter able to send continuous information were also discussed, practical application has not yet been achieved. Therefore, a telemetering system was developed and applied for analysis of occlusal force.
The transmitter was embeded in a removable partial denture with semiconductor strain gauges which were arranged to be sensitive to the vertical component of occlusal force applied to its metallic occlusal surface.
The transmitter consisted of a blocking oscillator intermitting the 7 MHz carrier from a Hartley type oscillator with rate of 5 kHz. Applied occlusal force change the resistance of strain gauge, which, in turn, was inverted into change in potential difference. The frequency of subcarrier was modulated by this potential difference.
The transmitted radio wave was received outside the oral cavity and demodulated into the potential difference proportional to occlusal force.
Appling the device the temporal pattern of masticatory force against to the denture containing the transmitter was recorded during mastication by teeth of the homolateral as well as contralateral side to the denture.
In contrast with the findings accepted widely, the pattern indicated that masticatory force was largest rather at the early stage of mastication and it decrease gradually during mastication.
From these results it was suggested that working sites of occlusal surfaces in every stroke might change according to the stages of mastication and central area of occlusal surface might work at final stage.

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On applying a logical orthogonal function, composed of two values to medical data processing, it was proved to be extremely effective in solving the following two problems.
One application of the function enabled the obtaining of signals which do not have instability of phase relations, which had been impossible to obtain through ordinary analog synthesis because of the generation of false biological signals. This method enabled us to carry out effectively biological system analysis by analog modelling.
Another application of the function enabled the clarification of the fact that an extremely sharp cut-off filter can be composed, which can eliminate noise, when noise is mingled with biological signals, even in the case of the noise frequency being extremely close to be frequency range of biological signals.

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An artificial heart is a pump system which has fluidic impedances, such as valves or connectors. Fluid flow in the artificial heart system is a turbulent flow with a high Reynolds number. Experiments with water and glycerin indicated that head losses of parts of artificial heart vary approximately with the square of velocity and led to the equation
H_L=K_IV²/2g=K_L8Q²/πgD⁴
V : velocity (cm/s), Q : flow rate (cm³/s), h_L, : head loss (cm), D : diameter (cm) in which K_L, the loss coefficient, is comparatively constant at high Reynolds number. Consequently, loss coefficient is constant, unaffected by viscosity and velocity of fluid.
The loss coefficient of an artificial heart can be calculated by the application of the Bernoulli's and continuity equations. The total head loss due to an inlet valve, an inlet connector, an outlet connector and an outlet valve was proved equal to the total of the head losses of each component.
The loss coefficients of valves and connectors measured in a circulation model, with water, glycerin and blood, were proved to be generally equal to the valves measured separately for each valve and connector.
When specifications of the artificial heart, such as cardiac output Q, systolic driving pressure h_out, diastolic sucking pressure h_in, mean blood pressure h_B, and systolic diastolic ratio k, are given, the loss coefficients of inlet and outlet valves and connectors are caluculated by the following equation.
K_I=2gS²hI/ (1+k) ²Q², hout=h_O+hB, K_O=2gS²k²h_O/ (1+k) ²Q²
K_I : inlet loss coefficient, Ko : outlet loss coefficient..
By calculating these loss coefficients, the size of valves and connectors of artificial heart can be determined.

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