Evaluation of a Combined Twondash; and Threendash;Dimensional Compression Method Using Human Visual Characteristics To Yield High-Quality 10colon;1 Compression of Cranial Computed Tomography Scans

摘要

RATIONALE AND OBJECTIVES.The compression of cranial computed tomography scans was improved by using independent intra- and interframe compression techniques.METHODS.For intraframe compression, an image was decomposed into four subimages, one subimagc was chosen as a reference subimage, and three of the subimages were predicted from the reference subimage. The prediction error was encoded with a classified vector quantizer (CVQ) based on human visual perception characteristics. Interframe redundancy is exploited by a displacement estimated interslice (DEI) algorithm that encodes the differences between reference subimages from adjacent slices. This combined DEIsol;CVQ method was subjectively evaluated by 13 radiologists under a blinded protocol, and was compared to the CVQ method alone, the DEI method alone, the original images, and to a standard intraframe discrete cosine transform (DCT) compression method.RESULTS.Only the combined DEIsol;CVQ method at 10colon;1 compression was not scored significantly different from the original images. At 15colon;1 compression, the DEIsol;CVQ method was scored significantly better than the 10colon;1 DCT and any other 15colon;1 compression methods.CONCLUSIONS.Compressed image quality is enhanced by exploiting inter- and intraframe redundancy, and by modelingsome characteristics of human visual perception. The DEIsol;CVQ method is well-suited for progressive transmission, and thus, holds potential in tcleradiology as well as picture archiving and communications systems.