Randoms variance reduction in 3D PET
Randoms variance reduction in 3D PET
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DOI：
10.1088/0031-9155/44/4/010
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发表时间：
1999-04-01
影响因子：
3.5
通讯作者：
Marsden, PK
中科院分区：
文献类型：
--
作者：
Badawi, RD;Miller, MP;Marsden, PK
在正电子发射断层扫描（PET）中，为了获得定量准确的数据，必须从测量信号中去除随机符合事件。用于估计特定响应线上的随机符合数的最广泛实施的技术是延迟符合通道方法。以这种方式获得的估计受到泊松噪声的影响，当从提示信号中减去估计时，泊松噪声传播到最终图像中。然而，这种噪声可能会减少，如果方差减少技术中使用的PET探测器的归一化应用到随机估计之前使用。我们已经调查了随机方差减少噪声等效计数（NEC）率在3D模式下操作的全身PET相机的影响。NEC率计算使用一系列的幻影代表的情况下，可能会遇到clinically.We还研究了三个随机方差减少方法（基于以前用于归一化算法）的属性，在其系统的准确性和方差减少的功效，无论是在幻影研究和体内。研究的那些算法不对随机重合的空间分布做出假设，给出了随机分布的最佳估计。使用具有有限轴向范围（10.8 cm）和大环直径（102 cm）的照相机，使用该技术获得的图像信噪比的增益范围从类似于5%到类似于15%，取决于对象大小、活动分布和视野中的活动量。如果将这种技术用于较大轴向范围和较小环直径的相机，则预期会有更大的增益。
In positron emission tomography (PET), random coincidence events must be removed from the measured signal in order to obtain quantitatively accurate data. The most widely implemented technique for estimating the number of random coincidences on a particular line of response is the delayed coincidence channel method. Estimates obtained in this way are subject to Poisson noise, which then propagates into the final image when the estimates are subtracted from the prompt signal. However, this noise may be reduced if variance reduction techniques similar to those used in normalization of PET detectors are applied to the randoms estimates prior to use.We have investigated the effects of randoms variance reduction on noise-equivalent count (NEC) rates on a whole-body PET camera operating in 3D mode. NEC rates were calculated using a range of phantoms representative of situations that might be encountered clinically.We have also investigated the properties of three randoms variance reduction methods (based on algorithms previously used for normalization) in terms of their systematic accuracy and their variance reduction efficacy, both in phantom studies and in vivo. Those algorithms investigated that do not make assumptions about the spatial distribution of random coincidences give the best estimates of the randoms distribution. With the camera used, which has a limited axial extent (10.8 cm) and a large ring diameter (102 cm), the gains in image signal-to-noise ratio obtained with this technique ranged from similar to 5% to similar to 15%, depending on object size, activity distribution and the amount of activity in the field of view. Larger gains would be expected if this technique were to be employed on cameras of greater axial extent and smaller ring diameter.