[Digital filing system for medical image data]

To establish practical, effective medical digital image filing systems, various problems remain to be solved. The authors focused on 2 such problems of great importance: image data compression and standard specifications for digital data storage. From a variety of image compression algorithms now available, 2D-Color Doppler image compression was clinically investigated using the Joint Photographic Expert Group (JPEG) method. In low grade compression, the images decompressed showed no significant alterations in image quality, however, in higher grades of compression attained through irreversible coding in the JPEG method, the images showed subtle but significant alterations: emergence of 2 kinds of artifact, i.e., borderline-artifact produced in the DCT procedures and pseudo color spots. The reproducibility of colors was found to be altered by changing the quantization table in the JPEG procedure. It was thought necessary to choose a proper quantization table and examine the DC coefficients (number of pixels) in the DCT procedure to attain practical 2D-Color Doppler image compression by the JPEG method. Although attempts in Japan are being made to establish common standards for electronic data storage, based on MEDIS, in an effort to promote standardization there are many problems to be solved before practical use is possible. To ensure common availability as required by the technical standards, it is necessary to organize minimum-required specifications into common standards and make them open to the public.