<title>Ultrasound image coding using shape-adaptive DCT and adaptive quantization</title>

Abstract

This paper presents a new scheme for compression of ultrasound images based on a variant of discrete cosine transform (DCT), called 'shape adaptive DCT' (SA DCT). This method exploits the fact that the clinical information of echo-cardiographic images does not occupy the whole image.SA DCT is a block based scheme that has ben designed specifically for encoding regions of arbitrary shape. Only the pixels belonging to the region of interest (ROI) are considered for coding. For each block, a mask specifying the ROI is also transmitted. Further coding efficiency can be gained by adapting the selection of the quantization table for each block. We report experimental results using eleven different quantization tables including two that are used in MPEG. Results of this scheme applied to echo-cardiographic ultrasound images are compared with those obtained using the classical DCT and the JPEG compression method. We show that the proposed method produces better results.