Comparison of noise equivalent count rates and image noise
Comparison of noise equivalent count rates and image noise
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DOI：
10.1109/tns.2005.858176
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发表时间：
2005-10-01
影响因子：
1.8
通讯作者：
Czernin, J
中科院分区：
文献类型：
--
作者：
Dahlbom, M;Schiepers, C;Czernin, J
本文的目的是研究噪声等效计数（NEC）率和重建图像的信噪比（S/N）之间的相关性。NEC率测定使用均匀的20和60厘米高的20厘米直径的圆柱体填充F-18。对体模进行二维和三维扫描。重建图像的噪声，为每一帧，估计使用自举方法。对于每个采集的帧，生成250个正弦图重复（分别为提示和随机），使用FBP和OSEM（2 i8 s和4 i8 s）重建。将图像过滤至最终图像分辨率为6 mm。从重建图像集生成平均值和标准偏差图像，从中计算5 cm中心ROL内的平均图像S/N（=平均值/标准偏差）。还研究了在从提示事件中减去之前对随机事件应用方差减小处理对图像噪声的影响。发现NEC与图像S/N的平方具有线性关系，其中发现的唯一差异是不同重建方法之间的斜率，这意味着每种重建算法特有的噪声特性的差异。线性关系也被发现在2-D和3-D采集模式，以及为不同的活动分布。随机处理显示出图像S/N的改善，与随机率的近无噪声估计一致。这些结果表明，NEC不仅是用于比较成像系统的计数率性能的度量，而且该度量还转化为用于比较图像噪声的度量。
The aim of this paper was to investigate the correlation between noise equivalent count (NEC) Rates and the signal-to-noise ratio (S/N) in the reconstructed images. NEC rates were determined using uniform 20- and 60-cm-tall 20-cm-diameter cylinders filled with F-18. The phantoms were scanned in both two-dimensional (2-D) and 3-D mode. The reconstructed image noise, for each frame, was estimated using the bootstrap method. For each acquired frame, 250 sinogram replicates were generated (prompts and randoms, separately), which were reconstructed using FBP and OSEM (2i8s and 4i8s). The images were filtered to a final image resolution of 6 mm. From the reconstructed image sets, mean and standard deviation images were generated, from which the average image S/N (=mean/standard deviation) was calculated within a 5-cm central ROL The effect of applying variance reduction processing on the random events, prior to subtraction from the prompt events, on the image noise was also investigated. The NEC was found to have a linear relationship to the square of the image S/N, where the only difference found was in the slope between different reconstruction methods, implying a difference in noise properties specific to each reconstruction algorithm. The linear relationship was also found in both 2-D and 3-D acquisition modes, as well as for the different activity distributions. The randoms processing showed an improvement in image S/N, consistent with a near noiseless estimate of the random rate. These results indicate that the NEC is not only a measure for comparing the count rate performance of imaging systems, but this measure also translates into a measure for comparing image noise.