EVALUATION OF A COMBINED 2-DIMENSIONAL AND 3-DIMENSIONAL COMPRESSION METHOD USING HUMAN VISUAL CHARACTERISTICS TO YIELD HIGH-QUALITY 10 1-COMPRESSION OF CRANIAL COMPUTED-TOMOGRAPHY SCANS/
Ms. Frank et al., EVALUATION OF A COMBINED 2-DIMENSIONAL AND 3-DIMENSIONAL COMPRESSION METHOD USING HUMAN VISUAL CHARACTERISTICS TO YIELD HIGH-QUALITY 10 1-COMPRESSION OF CRANIAL COMPUTED-TOMOGRAPHY SCANS/, Investigative radiology, 29(9), 1994, pp. 842-847
RATIONALE AND OBJECTIVES. The compression of cranial computed tomograp
hy scans was improved by using independent intra- and interframe compr
ession techniques. METHODS. For intraframe compression, an image was d
ecomposed into four subimages, one subimage 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 q
uantizer (CVQ) based on human visual perception characteristics. Inter
frame redundancy is exploited by a displacement estimated interslice (
DEI) algorithm that encodes the differences between reference subimage
s from adjacent slices. This combined DEI/CVQ method was subjectively
evaluated by 13 radiologists under a blinded protocol, and was compare
d to the CVQ method alone, the DEI method alone, the original images,
and to a standard intraframe discrete cosine transform (DCT) compressi
on method. RESULTS. Only the combined DEI/CVQ method at 10:1 compressi
on was not scored significantly different from the original images. At
15:1 compression, the DEI/CVQ method was scored significantly better
than the 10:1 DCT and any other 15:1 compression methods. CONCLUSIONS.
Compressed image quality is enhanced by exploiting inter- and intrafr
ame redundancy, and by modeling some characteristics of human visual p
erception. The DEI/CVQ method is well-suited for progressive transmiss
ion, and thus, holds potential in teleradiology as well as picture arc
hiving and communications systems.