Medical Imaging and Information Sciences

Angularly-Limited Computed Tomography

Satoshi KAWATA

1986 Volume 3 Issue 3 Pages 135-144
Published: 1986
Released on J-STAGE: August 27, 2012

DOIhttps://doi.org/10.11318/mii1984.3.135

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A Low Impedance and High Intensity Flash X-ray Generator for Biomedical Radiography

Hiroshi ISOBE, Eiichi SATO, Eiko TANIFUJI, Toshiaki FUJIYAMA, Sanae SA ...

1986 Volume 3 Issue 3 Pages 145-155
Published: 1986
Released on J-STAGE: August 27, 2012

DOIhttps://doi.org/10.11318/mii1984.3.145

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The construction of a low impedance and high intensity flash x-ray generator for biomedical radiography is described. This generator consisted of the following components: a high voltage power supply, a low impedance transmission line with a high voltage cozxial condenser (120 kV.0.15 μF), a compressed-gas (SF₆) gap switch with a small-sized trigger device operated by light through a fiber, a trigger delay device, a vacuum pump system, and two evacuated flash x-ray tubes each of a different type with eight coaxial cables. The flash x-ray generator could be used for condenser charging voltages of 50 to 120 kV. The exposure time was almost constant and its value was about 1 μs. The flash x-ray intensity was determined by the condenser charging voltage and the anode-cathode (A-C) space; the maximum intensities of the Type A and B tubes were about 100 and 200 mR at 1m/pulse, respectively. The dynamic image analysis of a tennis ball filled with contrast medium was performed by using the trigger delay system.

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Mathematical Model for the X-ray Film Characteristic Curves

Makoto SAITOH

1986 Volume 3 Issue 3 Pages 156-163
Published: 1986
Released on J-STAGE: August 27, 2012

DOIhttps://doi.org/10.11318/mii1984.3.156

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Baged on assumptions for the film grains sensitivity, we derived the mathematical model for the film photographic density curves that expresses the relation between exposure and photographic density. it is one of the parameters fitting models.
Using the equations obtained by a non-linear least squares method, about 1,300 sets were estimated the standard deviations. In result, a number of them were within 0.01 which is the accuracy of the densitometer.
We attempt to explain her the process provided the mathematical model, the method determined the parameters of it and some results.

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Similarity of Gastric Radiograms

Shigehiro FUKUSHIMA, Kyohei HAYASHI

1986 Volume 3 Issue 3 Pages 164-172
Published: 1986
Released on J-STAGE: August 27, 2012

DOIhttps://doi.org/10.11318/mii1984.3.164

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Similarity of gastric radiograms has been studied experimentally by applying the hierarchical clustering methods. The dendrograms obtained by the methods explain how each cluster was formed. Such dendrograms are presented for two kinds of features extracted (1) by two-dimensional orthogonal transform of the apex-regional image and (2) by geometric measurement and Fourier expansion of the contour of the stomach. It is concluded that the hierarchical clustering may be applicable to information retrieval and classification of pictorial data by morphological similarity.

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Granularity of X-ray Films and Random-dot Model

Kazuo TANAKA, Takao SASAKI

1986 Volume 3 Issue 3 Pages 173-181
Published: 1986
Released on J-STAGE: August 27, 2012

DOIhttps://doi.org/10.11318/mii1984.3.173

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It is known that the Wiener spectrum of film graininess of X-ray films cannot be explained by the conventional random-dot model (RDM) in low spatial frequencies. It is considered that the cause of this phenomenon is due to the effects of grain aggregations in the developed emulsion. The RDM does not take account of the effects of grain aggregations. In order to analyze the effects of grain aggregations, the RDM is extended by K. Tanaka and S. Uchida. In this paper, measured Wiener spectra of film graininess of X-ray films are compared with the theoretical results of this extended random-dot model (ERMA) and the RDM. Density fluctuations of films are measured by means of the microdensitometer and Wiener spectra are calculated by Blackman-Tukey's method. Microphotographs of films are also compared with computer-generated random-dot patterns. By using these methods, it is concluded that the ERDM is more appropriate than the RDM in describing properties of Wiener spectra of film graininess of X-ray films in low spatial frequencies.

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On Error-Free Data Compression for Digitized Images

Seihaku HIGUCHI, Katsumi MATSUNO

1986 Volume 3 Issue 3 Pages 182-190
Published: 1986
Released on J-STAGE: August 27, 2012

DOIhttps://doi.org/10.11318/mii1984.3.182

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Data sequences which are encountered in many situations of digital communications and data processing and are not specified as sequences from certain sources, usually display various structural regularities and allow for storage and time-saving techniques of data compression by using the regularities.
In this paper, a scheme of sequential data compression is presented. its performance is investigated and proved to be asymptotically optimal for mernoryless sources. The compression algorithm is used in another compression scheme, whose performance is also investigated and shown to be asymptotically optimal for first-order Markov sources. A simulation study is carried out for the illustration of algorithm developed here.

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