Effects of image preprocessing/resizing on diagnostic quality of compressed medical images [chest radiographs application]

The effect of prefiltering and resizing on the diagnostic quality of compressed images at various compression ratios is examined in this paper. A key object of the work is to get an insight on selecting an optimal combination of resolution and quantizer coarseness for a given ratio of compression of medical images. Test images were decimated by several decimation factors, and compressed to achieve a target file size. The decompressed images were assessed for their diagnostic quality. The authors' results demonstrate two things: (1) the higher sampling rates allow a quality margin that may offset the effects of subsequent quantization; and (2) gains in quality due to higher resolution levels may eventually be outstripped by the degrading effects of compression as the compression ratio increases. The result suggests a more gradual reduction in resolution would provide better control over loss of quality.