Lamare F, Turzo A, Bizais Y, Le Rest C Cheze, Visvikis D
U650 INSERM, Laboratoire du Traitement de l'information medicale (LaTIM), CHU Morvan, Université de Bretagne Occidentale, Brest, 29609, France.
Phys Med Biol. 2006 Feb 21;51(4):943-62. doi: 10.1088/0031-9155/51/4/013. Epub 2006 Feb 1.
A newly developed simulation toolkit, GATE (Geant4 Application for Tomographic Emission), was used to develop a Monte Carlo simulation of a fully three-dimensional (3D) clinical PET scanner. The Philips Allegro/GEMINI PET systems were simulated in order to (a) allow a detailed study of the parameters affecting the system's performance under various imaging conditions, (b) study the optimization and quantitative accuracy of emission acquisition protocols for dynamic and static imaging, and (c) further validate the potential of GATE for the simulation of clinical PET systems. A model of the detection system and its geometry was developed. The accuracy of the developed detection model was tested through the comparison of simulated and measured results obtained with the Allegro/GEMINI systems for a number of NEMA NU2-2001 performance protocols including spatial resolution, sensitivity and scatter fraction. In addition, an approximate model of the system's dead time at the level of detected single events and coincidences was developed in an attempt to simulate the count rate related performance characteristics of the scanner. The developed dead-time model was assessed under different imaging conditions using the count rate loss and noise equivalent count rates performance protocols of standard and modified NEMA NU2-2001 (whole body imaging conditions) and NEMA NU2-1994 (brain imaging conditions) comparing simulated with experimental measurements obtained with the Allegro/GEMINI PET systems. Finally, a reconstructed image quality protocol was used to assess the overall performance of the developed model. An agreement of <3% was obtained in scatter fraction, with a difference between 4% and 10% in the true and random coincidence count rates respectively, throughout a range of activity concentrations and under various imaging conditions, resulting in <8% differences between simulated and measured noise equivalent count rates performance. Finally, the image quality validation study revealed a good agreement in signal-to-noise ratio and contrast recovery coefficients for a number of different volume spheres and two different (clinical level based) tumour-to-background ratios. In conclusion, these results support the accurate modelling of the Philips Allegro/GEMINI PET systems using GATE in combination with a dead-time model for the signal flow description, which leads to an agreement of <10% in coincidence count rates under different imaging conditions and clinically relevant activity concentration levels.
一种新开发的模拟工具包GATE（用于断层发射的Geant4应用程序）被用于开发全三维（3D）临床正电子发射断层扫描（PET）扫描仪的蒙特卡罗模拟。对飞利浦Allegro/GEMINI PET系统进行了模拟，目的是：（a）详细研究在各种成像条件下影响系统性能的参数；（b）研究动态和静态成像发射采集协议的优化和定量准确性；（c）进一步验证GATE在临床PET系统模拟方面的潜力。开发了检测系统及其几何结构的模型。通过比较使用Allegro/GEMINI系统针对包括空间分辨率、灵敏度和散射分数在内的多个NEMA NU2 - 2001性能协议获得的模拟结果和测量结果，测试了所开发检测模型的准确性。此外，还开发了一个在检测到的单事件和符合事件层面上的系统死时间近似模型，以尝试模拟扫描仪的计数率相关性能特征。使用标准和修改后的NEMA NU2 - 2001（全身成像条件）以及NEMA NU2 - 1994（脑部成像条件）的计数率损失和噪声等效计数率性能协议，在不同成像条件下评估所开发的死时间模型，并将模拟结果与使用Allegro/GEMINI PET系统获得的实验测量结果进行比较。最后，使用重建图像质量协议评估所开发模型的整体性能。在一系列活度浓度和各种成像条件下，散射分数的一致性小于3%，真符合计数率和随机符合计数率之间的差异分别在4%和10%之间，导致模拟和测量的噪声等效计数率性能之间的差异小于8%。最后，图像质量验证研究表明，对于多个不同体积的球体以及两种不同的（基于临床水平的）肿瘤与背景比值，在信噪比和对比度恢复系数方面具有良好的一致性。总之，这些结果支持使用GATE结合死时间模型对飞利浦Allegro/GEMINI PET系统进行准确建模，以描述信号流，这导致在不同成像条件和临床相关活度浓度水平下符合计数率的一致性小于10%。
