Image Transforms, such as the S-Transform, provide a hierarchical representation of the image which is attractive as part of a data compression technique in a PACS environment. In this paper, the S-Transform is shown to be a special case of subband coding, thus characterizing the spectral behavior of the transform. The S-Transform decomposes the frequency plane into roughly octave spaced regions. The corresponding "octave" images in the spatial domain can be linearly combined with different weights in order to synthesize an enhanced image. This is a computationally efficient process which provides a great deal of flexibility in the specification of the enhancement MTF characteristic. Examples are shown of enhanced computed radiographs, comparing the results of our technique and unsharp masking.
"Hierarchical Image Decomposition And Filtering Using The S-Transform", Proc. SPIE 0914, Medical Imaging II, (27 June 1988); doi: 10.1117/12.968716; https://doi.org/10.1117/12.968716