A practical method for randoms subtraction in volume imaging PET from detector singles countrate measurements.
A practical method for randoms subtraction in volume imaging PET from detector singles countrate measurements.
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DOI：
10.1109/23.507257
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发表时间：
1996-06-01
影响因子：
1.8
通讯作者：
Karp, JS
中科院分区：
文献类型：
--
作者：
Smith, RJ;Karp, JS
由于单次计数率较高，体积成像 PET 扫描仪中的随机减法是一个重大问题。延迟符合方法需要对随机事件进行重复计数，并导致计数能力降低。由于探测器和重新分类的随机计数率之间的相机重合处理，基于探测器单个计数率的计算需要对计数率相关的生存时间和事件接受进行复杂的校正。轮廓分布方法已用于估计和减去散射和随机背景，但该方法是一种折衷方法，它将这两种背景源耦合在一起。为了避免这些问题并准确减去扫描数据中随机污染的分布和幅度，我们开发了一种替代的基于单数的方法。单次分布在探测器上进行测量，并用于构建随机分布正弦图。通过从体模校准生成的随机计数率与探测器单个计数率的查找表，将该分布缩放到适当的重新分类的随机计数率。通过此方法执行随机减法的优点是：(1) 相机死区时间不会增加，(2) 该方法补偿由于银行对上和非银行对的活动分布和相机的非均匀几何响应而导致的随机分布的不均匀性，以及 (3) 它处理独立于散射的随机减法，以便可以将不同的散射校正例程应用于数据。使用 F-18 以及单光子发射器 Cs-137 在高计数率下进行的体模测试（其中所有测量事件都是随机的）已经显示了可靠表示随机分布的方法。与轮廓分布法和延迟符合法进行了比较，新方法已成功应用于人体PET研究。
Randoms subtraction in a volume imaging PET scanner is a significant problem due to the high singles countrates experienced. The delayed coincidence method requires double counting of randoms events and results in a lowered countrate capability. Calculations based on detector singles countrates require complex corrections for countrate dependent livetime and event acceptance due to the camera coincidence processing between the detector and rebinned randoms countrates. The profile distribution method has been used to estimate and subtract both scatter and randoms background but this method is a compromise and couples these 2 sources of background together. In order to avoid these problems and provide accurate subtraction of both the distribution and magnitude of randoms contamination in the scan data we have developed an alternative singles based method. The singles distributions are measured across the detectors and are used to construct a randoms distribution sinogram. This distribution is scaled to the appropriate rebinned randoms countrate by means of a lookup table of randoms countrate vs detector singles countrate, generated from phantom calibrations. The advantages of performing randoms subtraction by this method are: (1) there is no increase in camera deadtime, (2) the method compensates for non-uniformities in randoms distributions due to both the activity distribution and non-uniform geometric response of the camera for on and off bankpairs, and (3) it deals with randoms subtraction independently of scatter so that different scatter correction routines may then be applied to the data. Phantom tests at high countrates with F-18, and also with a single-photon emitter, Cs-137, where all measured events are randoms, have shown the method to reliably represent the randoms distribution. Comparisons have been made with the profile distribution and delayed coincidence methods and the new method has been successfully applied to body PET studies.