Gatidis Sergios, Würslin Christian, Seith Ferdinand, Schäfer Jürgen F, la Fougère Christian, Nikolaou Konstantin, Schwenzer Nina F, Schmidt Holger
University of Tübingen, Department of Radiology Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany.
Hell J Nucl Med. 2016 Jan-Apr;19(1):15-8. doi: 10.1967/s002449910333. Epub 2016 Mar 1.
Optimization of tracer dose regimes in positron emission tomography (PET) imaging is a trade-off between diagnostic image quality and radiation exposure. The challenge lies in defining minimal tracer doses that still result in sufficient diagnostic image quality. In order to find such minimal doses, it would be useful to simulate tracer dose reduction as this would enable to study the effects of tracer dose reduction on image quality in single patients without repeated injections of different amounts of tracer. The aim of our study was to introduce and validate a method for simulation of low-dose PET images enabling direct comparison of different tracer doses in single patients and under constant influencing factors.
(18)F-fluoride PET data were acquired on a combined PET/magnetic resonance imaging (MRI) scanner. PET data were stored together with the temporal information of the occurrence of single events (list-mode format). A predefined proportion of PET events were then randomly deleted resulting in undersampled PET data. These data sets were subsequently reconstructed resulting in simulated low-dose PET images (retrospective undersampling of list-mode data). This approach was validated in phantom experiments by visual inspection and by comparison of PET quality metrics contrast recovery coefficient (CRC), background-variability (BV) and signal-to-noise ratio (SNR) of measured and simulated PET images for different activity concentrations. In addition, reduced-dose PET images of a clinical (18)F-FDG PET dataset were simulated using the proposed approach.
(18)F-PET image quality degraded with decreasing activity concentrations with comparable visual image characteristics in measured and in corresponding simulated PET images. This result was confirmed by quantification of image quality metrics. CRC, SNR and BV showed concordant behavior with decreasing activity concentrations for measured and for corresponding simulated PET images. Simulation of dose-reduced datasets based on clinical (18)F-FDG PET data demonstrated the clinical applicability of the proposed data.
Simulation of PET tracer dose reduction is possible with retrospective undersampling of list-mode data. Resulting simulated low-dose images have equivalent characteristics with PET images actually measured at lower doses and can be used to derive optimal tracer dose regimes.
在正电子发射断层扫描（PET）成像中优化示踪剂剂量方案是在诊断图像质量和辐射暴露之间进行权衡。挑战在于确定仍能产生足够诊断图像质量的最小示踪剂剂量。为了找到这样的最小剂量，模拟示踪剂剂量减少将是有用的，因为这将能够在不重复注射不同量示踪剂的情况下研究单个患者中示踪剂剂量减少对图像质量的影响。我们研究的目的是引入并验证一种用于模拟低剂量PET图像的方法，该方法能够在单个患者中且在恒定影响因素下直接比较不同的示踪剂剂量。
在一台PET/磁共振成像（MRI）联合扫描仪上采集（18）F-氟化物PET数据。PET数据与单个事件发生的时间信息一起存储（列表模式格式）。然后随机删除预定义比例的PET事件，从而得到欠采样的PET数据。随后对这些数据集进行重建，得到模拟的低剂量PET图像（列表模式数据的回顾性欠采样）。通过目视检查以及比较不同活度浓度下测量的和模拟的PET图像的PET质量指标对比度恢复系数（CRC）、背景变异性（BV）和信噪比（SNR），在体模实验中验证了该方法。此外，使用所提出的方法模拟了临床（18）F-FDG PET数据集的低剂量PET图像。
随着活度浓度降低，（18）F-PET图像质量下降，测量的PET图像和相应模拟的PET图像具有可比的视觉图像特征。通过图像质量指标的量化证实了这一结果。对于测量的和相应模拟的PET图像，CRC、SNR和BV随着活度浓度降低表现出一致的行为。基于临床（18）F-FDG PET数据模拟剂量减少的数据集证明了所提出数据的临床适用性。
通过对列表模式数据进行回顾性欠采样可以模拟PET示踪剂剂量减少。所得的模拟低剂量图像与在较低剂量下实际测量的PET图像具有等效特征，可用于推导最佳示踪剂剂量方案。
