Effective count rates for PET scanners with reduced and extended axial field of view
Effective count rates for PET scanners with reduced and extended axial field of view
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DOI：
10.1088/0031-9155/56/12/011
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发表时间：
2011-06-21
影响因子：
3.5
通讯作者：
Kinahan, P. E.
中科院分区：
文献类型：
--
作者：
MacDonald, L. R.;Harrison, R. L.;Kinahan, P. E.
我们研究了PET扫描仪的噪声等效计数（NEC）和轴向视野（AFOV）之间的关系，AFOV范围为当前临床扫描仪的一半到两倍。具有更长或更短AFOV的PET扫描仪可以满足不同的临床需求，具体取决于检查量和现场经济性。使用先前验证的Monte Carlo模拟，我们模拟了直径为88 cm的PET环与2、4、6和8个探测器块环（AFOV 7.8、15.5、23.3和31.0 cm）的真实、分散和随机符合计数率。将全3D采集模式与全准直（2D）和部分准直（2.5D）模式进行了比较。对200 cm长版本的20 cm直径NEMA计数率体模和基于患者扫描的拟人物体估计计数率。我们估计从测量的计数率数据的扫描仪的生存时间特性，并将该估计应用于模拟结果，以获得NEC作为对象活动的函数。我们发现NEC在3D模式下是AFOV的二次函数，在2D模式下是线性增加的。对于临床相关活动，部分准直在2-阻滞系统上提供了最高的总体NEC，全3D模式在8-阻滞系统上提供了最高的NEC。在4-和6-块系统上，3D模式NEC最高，在拟人体模中接近300 MBq，高于该值3D NEC迅速下降，2.5D NEC最高。当使用最佳准直时，对于8、6、4和2块环系统，在典型肿瘤学检查中达到与当前临床实践相匹配的NEC密度的预计总扫描时间平均为9、15、24和61分钟。增加AFOV应提供大于NEC比例的增加，可能有利于患者吞吐量与成本比。相反，通过使用适当的准直，双环（7.8 cm AFOV）系统可以在长但可行的扫描时间内采集全身扫描，达到与当前标准相当的NEC密度水平。
We investigated the relationship between noise equivalent count (NEC) and axial field of view (AFOV) for PET scanners with AFOVs ranging from one-half to twice those of current clinical scanners. PET scanners with longer or shorter AFOVs could fulfill different clinical needs depending on exam volumes and site economics. Using previously validated Monte Carlo simulations, we modeled true, scattered and random coincidence counting rates for a PET ring diameter of 88 cm with 2, 4, 6, and 8 rings of detector blocks (AFOV 7.8, 15.5, 23.3, and 31.0 cm). Fully 3D acquisition mode was compared to full collimation (2D) and partial collimation (2.5D) modes. Counting rates were estimated for a 200 cm long version of the 20 cm diameter NEMA count-rate phantom and for an anthropomorphic object based on a patient scan. We estimated the live-time characteristics of the scanner from measured count-rate data and applied that estimate to the simulated results to obtain NEC as a function of object activity. We found NEC increased as a quadratic function of AFOV for 3D mode, and linearly in 2D mode. Partial collimation provided the highest overall NEC on the 2-block system and fully 3D mode provided the highest NEC on the 8-block system for clinically relevant activities. On the 4-, and 6-block systems 3D mode NEC was highest up to similar to 300 MBq in the anthropomorphic phantom, above which 3D NEC dropped rapidly, and 2.5D NEC was highest. Projected total scan time to achieve NEC-density that matches current clinical practice in a typical oncology exam averaged 9, 15, 24, and 61 min for the 8-, 6-, 4-, and 2-block ring systems, when using optimal collimation. Increasing the AFOV should provide a greater than proportional increase in NEC, potentially benefiting patient throughput-to-cost ratio. Conversely, by using appropriate collimation, a two-ring (7.8 cm AFOV) system could acquire whole-body scans achieving NEC-density levels comparable to current standards within long, but feasible, scan times.