BACKGROUND. Digital PET scanners with increased sensitivity may allow shorter scan acquisition times or reductions in administered radiopharmaceutical activities.

OBJECTIVE. The purpose of this study was to evaluate in children and young adults the impact of shorter simulated acquisition times on the quality of whole-body FDG PET images obtained using a digital PET/CT system.

METHODS. This retrospective study included 27 children and young adults (nine male and 18 female patients) who underwent clinically indicated whole-body FDG PET/CT examinations performed using a 25-cm axial FOV PET/CT system at 90 s per bed position (expressed hereafter as seconds per bed). Raw list-mode data were reprocessed to simulate acquisition times of 60, 55, 50, 45, 40, and 30 s/bed. Three radiologists independently reviewed reconstructed images and assigned Likert scores for lesion conspicuity, normal structure conspicuity, image quality, and image noise. A separate observer recorded the SUV_max, SUV_mean, and SD of the SUV (SUV_SD) for liver, thigh, and the most FDG-avid lesion. The SUV_SD/SUV_mean (the SUV_SD divided by the SUV_mean) was calculated as a surrogate of image noise. ANOVA, the Friedman test, and the Dunn test were used to compare qualitative measures (combining reader scores) and SUV measurements.

RESULTS. The mean patient age was 10.8 ± 8.3 (SD) years, mean BMI was 18.7 ± 2.9, and mean administered FDG activity was 4.44 ± 0.37 MBq/kg (0.12 ± 0.01 mCi/kg). No qualitative measure showed a significant difference versus 90 s/bed for the simulated acquisition at 60 s/bed (all p > .05). Significant differences (all p < .05) versus 90 s/bed were observed for lesion conspicuity at at most 40 s/bed, conspicuity of normal structures and overall image quality at at most 45 s/bed, and image noise at at most 55 s/bed. SUV_mean was not significantly different from 90 s/bed for any site for any reduced-count simulation (all p > .05). SUV_SD/SUV_mean and SUV_max showed gradual increases with decreasing acquisition times and were significantly different from 90 s/bed only for liver at 60 s/bed (for SUV_max: 1.00 ± 0.00 vs 1.05 ± 0.03, p = .02; for SUV_SD/SUV_mean: 0.09 ± 0.02 vs 0.11 ± 0.02, p = .04).

CONCLUSION. Favorable findings for the simulated acquisition at 60 s/bed suggest that, in children and young adults who undergo imaging performed using a 25-cm FOV digital PET scanner, acquisition time or administered FDG activity may be decreased by approximately 33% from the clinical standard without significantly impacting image quality.

CLINICAL IMPACT. A 25-cm axial FOV digital scanner may allow FDG PET/CT examinations to be performed with reduced radiation exposure or faster scan acquisition times.

背景。具有更高灵敏度的数字 PET 扫描仪可以缩短扫描采集时间或减少所管理的放射性药物活动。

客观的。本研究的目的是在儿童和年轻人中评估较短的模拟采集时间对使用数字 PET/CT 系统获得的全身 FDG PET 图像质量的影响。

方法。这项回顾性研究包括 27 名儿童和年轻人（9 名男性和 18 名女性患者），他们接受了临床指征的全身 FDG PET/CT 检查，使用 25 厘米轴向 FOV PET/CT 系统，每个床位 90 秒（下文表示）每张床的秒数）。原始列表模式数据被重新处理以模拟 60、55、50、45、40 和 30 秒/床的采集时间。三名放射科医生独立审查重建图像，并为病变显着性、正常结构显着性、图像质量和图像噪声分配李克特评分。一位单独的观察员记录了肝脏、大腿和最富含 FDG 的病变的 SUV_最大值、SUV_平均值和 SUV (SUV _{SD ) 的标准差。}SUV _SD /SUV_意思（SUV _SD除以 SUV_平均值）被计算为图像噪声的替代物。方差分析、弗里德曼检验和邓恩检验用于比较定性测量（结合读者分数）和 SUV 测量。

结果。平均患者年龄为 10.8 ± 8.3 (SD) 岁，平均 BMI 为 18.7 ± 2.9，平均给予的 FDG 活性为 4.44 ± 0.37 MBq/kg (0.12 ± 0.01 mCi/kg)。对于 60 秒/床的模拟采集，没有定性测量显示与 90 秒/床有显着差异（所有p > .05）。在最多 40 秒/床的病变显着性、最多 45 秒/床的正常结构和整体图像质量的显着性以及最多 55 秒的图像噪声方面，观察到显着差异（所有 p < .05）与 90 秒/床床。对于任何减少计数模拟的任何站点， SUV平均值与 90 秒/床没有显着差异（所有_p > .05）。SUV _SD /SUV_均值和 SUV_最大值显示随着采集时间的减少而逐渐增加，并且与 90 秒/床显着不同，仅肝脏为 60 秒/床（对于 SUV_最大值：1.00 ± 0.00 对比 1.05 ± 0.03，p = .02；对于 SUV _SD /SUV_平均值：0.09 ± 0.02 对比 0.11 ± 0.02，p = .04）。

结论。以 60 秒/床进行模拟采集的有利结果表明，在使用 25 厘米 FOV 数字 PET 扫描仪进行成像的儿童和年轻人中，采集时间或施用的 FDG 活性可能比临床标准减少约 33%在不显着影响图像质量的情况下。

临床影响。25 厘米轴向 FOV 数字扫描仪可以在减少辐射暴露或加快扫描采集时间的情况下进行 FDG PET/CT 检查。