基于小波变换的三维医学图象压缩技术的研究

Medical Image Compression Based on Three Dimensional Wavelet Transformation In PACS

满足临床诊断要求的医学影像无失真压缩编码技术的研究是图象压缩编码研究的新领域 ,也是 PACS系统和远程医疗诊断系统研究的热点之一 .该文正是以 CT,MRI等医疗成像设备在临床应用时一次检查产生的人体某一部位的多帧断层图象而形成的序列图象组为对象 ,选取目前编码领域最具潜力的小波变换技术 ,并将小波变换由二维推广至三维 ,同时将二维医学序列图象组视为三维图象而开展的医学影像编码技术研究 .实验结果表明 ,在经临床医师确认的失真门限附近 ,该技术可以将压缩比提高 2 0 %～ 47%左右 ,这对实际应用是十分有利的 .

In PACS,CT and MRI scanners provided lots of 3D images every day. For this reason, JPEG ,as a 2D image coding technology is not compatible. In this paper, a three dimensional medical images compression method based on 3D wavelet transform is proposed. At first, various filter banks in the slice direction are used and the results of rebuild images are compared to find the best filter bank for 3D transform. Then using MSE as performance index, the author presents a new 3D best quantization method independently. And DPCM is replaced by S+P transform in low resolution subband for enhance coding efficiency. Furthermore, we test various entropy coding methods, based on which a synthesis entropy coding method is found. We think it best fit for wavelet transform coding. At last, an integrity 3D wavelet transform coding method is proposed. We test out the method on lots of 3D images, the results show that this method can elevate compression ratio region from 20% to 47%, compared with JPEG or 2D wavelet transform. This 3D coding method can offset the failure of 2D coding method in PACS perfectly.