Applied Medical Image Processing, 2nd Edition

Chapter 7

Spatial Transforms

Wolfgang Birkfellner

7.1 Discretization – Resolution and Artifacts

Ever since Chapter 3, we are aware that images consist of 2D or 3D image elements. These elements are, by their nature, discrete. A change in image size therefore introduces artifacts, which may be considered rounding errors. Figure 7.1 gives an illustration. The original image is a PET-scan with 128 × 128 pixels in-plane resolution of a gynecological tumor located in the pelvis. The left part of the image was resized without interpolation – the single pixels appear blocky and enlarged. If we apply an interpolation procedure, which distributes the pixel intensities in a more sophisticated manner, we get the result on the right hand side. In short, ...