Many images are generated by medical equipment and the number of images to be stored increases yearly. To cope with the large digital storage and transmission requirements, data compression techniques have been studied. In the present study, grayscale data (2 bytes/pixel) were divided into high bytes and low bytes, and then the original medical images were also divided into high byte (lbyte/pixel format) and low byte (lbyte/pixel format) images. Inter-frame coding with and without division into high and low byte images was applied to MDCT images. Prediction (inter-frame) coding is a very common method to compress sequence images. The division process can be added to inter-frame coding easily. The compression ratio of the archived file produced by application of Lemple-Ziv compression and prediction coding with the division process was 0.39 at 700 images.

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We designed and fabricated a generator of mono-energetic electrons for the response test of charged particle detectors, which is used to measure fragmented particles of the carbon beam for cancer therapy. Mono-energetic electrons are extracted from ⁹⁰Sr by analyzing the energy of beta rays in the generator with a magnetic field. We evaluated performance parameters of the generator such as the absolute energy, the energy resolution and the counting rates of extracted electrons. The generator supplies mono-energetic electrons from 0.5MeV to 1.7MeV with the energy resolution of 20% in FWHM at higher energies than 1.0MeV. The counting rate of electrons is 400cpm at the maximum when the activity of ⁹⁰Sr is 298kBq. The generator was used to measure responses of fragmented-particle detectors and to determine the threshold energy of the detectors. We evaluated the dependence of pulse height variation on the detector position and the threshold energy by using the generator. We concluded this generator is useful for the response test of general charged particle detectors.

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Recently, a few types of step-wedges for bootstrap sensitometry with a mammographic screen-film system have been proposed. In this study, the bootstrap sensitometry with the mammographic screen-film system was studied for two types of aluminum step-wedges. Characteristic curves were determined using mammographic and general radiographic aluminum step-wedges devised to prevent scattered X-rays generated from one step penetrating into the region of another one, and dependence of the characteristic curves on the wedges was also discussed. No difference was found in the characteristic curves due to the difference in the step-wedges for mammography and general radiography although there was a slight difference in shape at the shoulder portion for the two types of step-wedges. Therefore, it was concluded that aluminum step-wedges for mammography and general radiography could be employed in bootstrap sensitometry with the mammographic screen-film system.

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