JPEG2000有损压缩对核医学图像的压缩效果的客观定量研究

从线源图像获得线源扩展函数、调制转移函数和峰-总计数比等参数,定量研究JPEG 2000有损压缩对核医学图像的压缩效果,并与实际分辨率图像和模拟分辨率图像的压缩效果进行对比。实验发现,随压缩比的增加,峰-总计数比曲线逐步下降,且噪声水平越高,曲线下降越快;但调制转移函数曲线和线源扩展函数曲线的半高宽无明显变化;随压缩比的增加,分辨率图像上可辨认出的条纹逐渐减少。实验结果表明,在压缩比和噪声水平变化时,峰-总计数比的变化与图像质量的变化规律一致,是用于图像压缩效果评价的较好的客观定量参数。

Objective and Quantitative Study on the Effect of Lossy JPEG2000 Compression of Nuclear Medicine Image

To objectively and quantitatively study the effect of JPEG2000 lossy compression of nuclear medicine image,line source images of various noise levels, actual quadrant-bar phantom images and simulated quadrant-bar phantom images of various noise levels were compressed using a JPEG2000 plug-in at 10:1 to 50:1 with a 10:1 step.Modulation transfer function(MTF),full width at half-maximum(FWHM) and the peak to total count ratio(PTCR) of line spread function of the simulated line source images were analyzed quantitatively.Image quality of the quadrant-bar phantom images was visually evaluated according to quality control procedures and the result was used to verify the quantitative analysis.It was observed that PTCR decreased as compression ratio increased and the higher the noise level,the faster PTCR decreased,which was in accordance with the increase of the width of the smallest bars that can be visually resolved in the actual quadrant-bar phantom images and simulated quadrant-bar phantom images.On the other hand,no significant change of MTF and FWHM was observed as compression ratio increased.It was concluded that PTCR may serve as an objectively quantitative metrics of image quality assessment.