practicable techniques, which could be exploited. Differential pulse code modulation (DPCM)[41 predictive coding method is predominant in lossless.
Proceedings of ICSP ‘98
Lossless Compression of DSA Image Sequence Based on D2PCM Coder Ji Zhen, Mou Xuanqin, Jiang Yifeng, Cai Yuanlong Image Processing Center, Xi’an Jiaotong Univ. Xi’an, P.R.C., 710049
ABSTRACT: A novel D~PCM compression technique has been developed in this paper for more effective lossless compression of DSA (Digital Subtraction Angiography) image sequence, in which the correlation between subtraction images remains meaningful. By applying the lossless DPCM coder to the subtraction image, it constitutes a two-order differential coding scheme with the time variable. This proposed method is able to sufficiently reduce the temporal-space correlation. Higher compression ratio is achieved than previous techniques. The computational time and space also prove practicable and robust in real life application.
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I INTRODUCTION Medical image compression has been mainly concerned with lossless coding techniques [‘I, which ensure that all significant information for diagnostic purposes is retained in the reconstructed images wi!& the compression ratio of around 2:l.The Digital Image and Communications in Medicine proposed standard (DICOM3),that adopted by the American College of Radiology and National Electrical Manufacturing Association(ACR-NEMA), includes lossless coding and compression of medical images. However, recent studies concerning “Visually lossless” and “Information preserving” indicate that the reconstruction error is accepted from a medical point of view. ACR-NEMA announced a call for proposals for lossy compression that has been included in DICOM3.0 in 1995. This class of compression techniques is subjective definitions and extreme caution msut be taken into considerance in P.R.C,where the criteria remains ambiguous and many complex
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legal and regulatory issues would arise. The objective of compressing images is to reduce the data volume and achieve a low bit rate. Compressing a digital medical image can facilitate its storage and transmission. With regard to the legislation problems, physician prefers diagnosing with uncorrupted medical image. The popular lossless coding schemes includes Huffinan, arithmetic, run-length encoding (RLE) and LZW[*].More effective coding method is desired for the fast growth of PACS (Picture Archiving and Communication System) and Teleradiology. Acquisition of 3-D and 4-D medical image sequences are becoming more usual nowadays, especially in the case of dynamic studies with MRI,CT, DSA, PET. Thus another challenge is to enable multi-dimensional medical images coding providing fast processing time and reasonable performance. A new lossless compression method is proposed for the image sequence generated by DSA (Digital SubtractionAngiography ) apparatus, which is now common as X-ray, CT. Compressing an image sequence is equal to compression of 3D data, which contains both space and time redundance. The well-known MPEGr3]provides the perfect resolution of the lossy coding of image sequence. It has proved effective and proposed many practicable techniques, which could be exploited. Differential pulse code modulation (DPCM)[41 predictive coding method is predominant in lossless compression. In this paper, high order(2-order) DPCM coder is introduced that can exploit the correlation between one-order differential images and two-order ones to benefits of compression, which has highly competitive compression performance and remains practical. We present the description of this proposed lossless image sequence coder in followed sections.
n. CHARACTERISTICS OF DSA IMAGES
Image compression techniques usually consist of concrete mathematical models. In practical applications, the specific images, for which the available priori knowledge could be exploited in order to develop an optimized compression scheme. A typical DSA image sequence is shown in Figure 1,which consists of
(a) when K
