Abstract: An image compression apparatus for compressing medical information such as X-ray image data divides the image data into blocks and extracts the region of interest from the image data, excluding the background portion. The image data blocks containing the region of interest are orthogonally transformed by discrete cosine transformation for forming a bit allocation table. The bit assignments in the bit allocation table for the orthogonally-transformed coefficients are adapted only for the image data containing the region of interest. The original image data blocks are orthogonally transformed and quantized according to the bit allocation table to obtain the compressed image data.

Abstract: A spatial filter has a plurality of uniformly weighting spatial filters for defining as pixel data of a given pixel a value corresponding to a sum of pixel data in a predetermined square area near the given pixel. The characteristics of these uniformly weighting spatial filters are linearly coupled to obtain substantially circular filter characteristics.

Abstract: There is provided a superposed image display device to display image signals from a plurality of image diagnostic apparatuses such as an X-ray CT apparatus, NMR CT apparatus, etc. This display device comprises memories to store the image signals from the CT apparatuses and NMR CT apparatus, multipliers to multiply the image signals read out from the memories by K1 and K2, an adder to add the output signals of the multipliers, and a display device to display the output signal of the adder.

Abstract: In a digital radiographic technique, a spatial filtering process has been widely introduced. The image data processing apparatus includes a first storage device for storing original image data in a digital form which is used for medical diagnosis. A filtering device is provided for performing a filtering function to the original image data so as to control spatial frequency characteristics of the original image data. A second storage device is used for storing the filtered image data derived from the filtering device, and a first multiplexer device is provided for multiplying the filtered image data which is stored in the second storage device, by a first parameter so as to give a first weighted value to the filtered image data.