基于JPEG技术的CT图像压缩方法的研究

CT图像在医学影像诊断中占有重要地位，CT图像压缩技术是PACS系统的重要组成部分。JPEG静止图像压缩标准目前已成为一种广泛应用的图像压缩技术。JPEG充分利用人眼的视觉特性，对DCT系数的低频系数进行细量化，而对高频系数进行粗量化，但未对图像的边缘特征进行特殊的处理。而图像的部分边缘特征又正是隐含于DCT高频系数中。文中从图像边缘信息的谱分析入手，通过理论推导及实例分析得到平直单边缘图像子块其DCT系数能量的分布规律，并以此为理论基础设计出JPEG中DCT系数量化表(Q表)，实验结果表明该Q表对非平直边缘图象子块没有影响，而对含有平直边缘图像子块的边缘信息进行了有效的保持。

A STUDY OF CT IMAGE COMPRESSION BASED ON JPEG TECHNOLOGY

CT Image plays an important role in medical imaging diagnosis. CT Image compression technology is the important part of PACS system. JPEG image compression standard has now gained wide applications, which takes advantage of the features of human visual system (HVS). It quantizes the low frequency DCT coefficients with fine level and the high frequency DCT coefficients with coarse level, But JPEG does not specifically process the image edges, which are partly hiding in high frequency DCT coefficients. On analysing the spectrum of image edge features, this paper got the energy distribution of DCT coefficients of a image subblock with a single straight edge through theoretical deduction and illustration by numerical examples. We designed a quantization table (Q table) in JPEG. Experiments showed that the Q table did not influence the image subblock with no single straight edge and could retain the image edge of image subblock with a single edge effectively.