<title>Volumetric image compression by 3D discrete wavelet transform (DWT)</title>

Abstract

The newly developed discrete wavelet transform (DWT) compression method is far superior to previous full frame discrete cosine transform (FFDCT) as well as industrial standard JPEG. Due to its localization properties both in spatial and transform domain, the quantization error introduced in DWT will not propagate globally as in FFDCT. Also DWT transform is a global technique that avoids the JPEG type block artifacts. As in all techniques, correlation among pixels makes compression possible. In volumetric image sets, such as CT and MR, inter-slice correlation can be exploited in addition to in-slice correlation. In this 3D DWT study, inter- slice correlation has also been investigated for CT and MR image set. Different numbers of slices are grouped together to perform wavelet transform in the transaxiale direction as a mean of testing relationship between correlation and compression efficiency. The 3D DWT is developed on UNIX platform. Significant higher compression ratio is achieved by compressing CT data as a volume versus one slice at a time. DWT is an excellent technique for exploiting inter-slice correlation to gain additional compression efficiency.