Energy compaction capability of DCT and DHT with CT image constraints

Since computerized tomography (CT) images have general structures consisting of an approximately elliptical region containing almost all of the image energy and are bounded by a region in which the image intensity is essential zero, the property must be introduced into the source model for performing transform coding analysis. For 3-D CT image data sets, in order to take advantage of the time-domain correlation between contiguous images, the difference between consecutive images is encoded instead of the original one. The energy compaction capabilities of DCT and DHT using a 2-D source model (for spatial dependence) and a difference model (for time dependence) with boundary constraints, both separable and non-separable, are explored. Experiments are performed to verify that DHT is suitable to be used in transform coding for CT data.