双能量乳腺X射线成像噪声分析与评价方法

针对双能量乳腺X射线成像结果易受到成像噪声影响的问题,提出了一种新的用于评价成像噪声对双能量计算结果影响的方法.该方法首先采用乳腺体模在两台临床常用的乳腺X射线成像系统中用双能量曝光,计算出成像噪声大小,并根据双能量成像物理模型推导出双能量计算结果对成像噪声的敏感度指标公式,然后依据公式和成像噪声水平评价敏感度大小.使用该评价方法对成像噪声引起的钙化图像背景区域的波动值以及钙化点的对比度信噪比值进行研究,仿真结果表明,成像噪声对双能量计算结果的影响较大,对于Essential系统,成像噪声会给钙化图像背景区域带来100～120μm的波动；对于DS系统,波动为160～200μm.Essential系统的性能明显优于DS系统,更适合于双能量乳腺X射线成像.

An Analysis and Evaluation Method for Imaging Noise in Dual-Energy Digital Mammography

Since the results of dual-energy digital mammography(DEDM) are always influenced by image noise,a new algorithm is presented to evaluate the imaging noise effects and is verified on clinical systems.A breast phantom is exposed using the dual-energy(DE) technique on two clinical systems and then the imaging noise is calculated.A sensitivity formula of DE calcification signal to imaging noise is deduced based on DEDM physical model and is used to evaluate sensitivities.Imaged breast with different calcification clusters is simulated and a calcification image is generated by using an inverse-map function.With this proposed algorithm,evaluations are performed by comparing the root-mean-square of calcification signal fluctuations in background regions with the contrast-noise-ratio of calcification signals in clusters.The simulation results show that the imaging noise has a big impact on DEDM calcification signals,and causes 100~120 μm calcification signal fluctuations on GE Senographe Essential system and 160~200 μm fluctuations on GE Senographe DS system.It shows that the essential system is more effective in DEDM.