Outline of recent activities of research and development in the field of medical image information system is reported. The results of our activity are listed in references (1)-(30). Repertory of our activities is extended from medical image processing to PACS development, PACS for radiotherapy, diagnostic reporting system, image perception practice and database construction for radiation oncology.
Feature of our R&D is medical application of existed technology factors, rather than basic research. Cooperation with School of Medicine and Faculty of Engineering of Osaka University are deployed recently for clinical application of technologies and physics at large. As an example of our recent activities, design and development of PACS for Osaka University Hospital is described. Also importance and significance of technology assessment is stated.

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Image processings were applied to enhance gastric cancer radiographs for better visualization of the malignant lesion. Utilized image processings were grey scale transformation, histogram equalization, edge enhancement (Sobel operator) and high-pass filter (unsharp masking). Grey scale transformation improved image quality for survey of a gastric lesion. Histogram equalization improved image quality of the underexposed or thin barium coating mucosa. Sobel operator was able to enhance linear or curved margin and consequently suppress the rest. High-pass filter with unsharp masking was superior to visualization of texture pattern on the gastric mucosa. The image enhancement contributed to clarify tumor occurrence on the non-pathologic or pathologic mucosa. The results suggest that, with these image processings, malignant changes on the gastric mucosa may be detected in their early stage. Further clinical application will be expected in the mass survey radiological examination for gastric cancer.

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For the evaluation of tube voltage waveforms, the tube voltage ripple and tube voltage peak number have been used. However, for high frequency waveforms of tube voltage such as those of an inverter type X-ray generator, ripple and peak number are insufficient. Then, we suggest the frequency analysis method of tube voltage waveforms. In this method, waveforms are analyzed by using fast Fourier transform (FFT). The method is convenient to the assessment of distortion and frequency of tube voltage waveforms, especially useful for the detailed evaluation of an inverter type X-ray generator. We also measured the overall value of power spectra by using FFT analysis, and there is a good possibility that it is useful for the evaluation of X-ray beam quality.

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We performed the Coltman's correction by computer simulation and investigated the number of terms should be used for correction as well as the computation error. In the range of up to 100correction terms, we examined the difference between two computation methods, i. e., single precision and double precision, and compared the calculated results obtained with and without an arithmetic operation processor, also, order of addition operation. We found that the obtained MTF values at zero spatial frequency are similar. Therefore we may conclude that no error due to various computation methods occurs. Moreover, the calculated MTF values at zero spatial frequency are the closest to unity when 58 terms,60 terms, and 62 terms are used. And the corrected results obtained using 58 terms and 62 terms showed no significant difference. Thus we may state that 58 terms are sufficient for correction.

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The bremsstrahlung spectrum from a thick tungsten target is calculated using Monte Carlo method, taking into account energy-loss straggling of electrons in the target. Landau distribution and Gaussian distribution are applied to energy-loss straggling of electrons. The calculated spectra using Landau distribution are in good agreement with Birch-Marshall data of bremsstrahlung spectra, without any modification on the Bethe-Heitler cross section with an empirical correction factor discussed by Koch and Motz.

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