Department of Nuclear Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, 200032, Shanghai, P.R. China.
Institute of Nuclear Medicine, Fudan University, Shanghai, 200032, China.
Cancer Imaging. 2022 Dec 29;22(1):78. doi: 10.1186/s40644-022-00517-8.
The injection activity of tracer, acquisition time, patient-specific photon attenuation, and large body mass, can influence on image quality. Fixed acquisition time and body mass related injection activity in clinical practice results in a large difference in image quality. Thus, this study proposes a patient-specific acquisition time regimen of Ga-DOTATATE total-body positron emission tomography-computed tomography (PET/CT) to counteract the influence of body mass (BM, kg) on image quality, and acquire an acceptable and constant image of patients with neuroendocrine tumors (NETs).
The development cohort consisting of 19 consecutive patients with full activity (88.7-204.9 MBq, 2.0 ± 0.1 MBq/kg) was to establish the acquisition time regimen. The liver SNR (signal-to-noise ratio, SNR) was normalized (SNR) by the product of injected activity (MBq) and acquisition time (min). Fitting of SNR against body mass (BM, kg) in linear correlation was performed. Subjective assessment of image quality was performed using a 5-point Likert scale to determine the acceptable threshold of SNR, and an optimized acquisition regimen based on BM was proposed, and validated its feasibility through the validation cohort of 57 consecutive NET patients with half activity (66.9 ± 11.3 MBq, 1.0 ± 0.1 MBq/kg) and a fixed acquisition time regimen.
The linear correlation (R = 0.63) between SNR and BM (kg) was SNR = -0.01BM + 1.50. The threshold SNR of acceptable image quality was 11.2. The patient-specific variable acquisition time regimen was determined as: t (min) = 125.4/(injective activity)(-0.01*BM + 1.50). Based on that proposed regimen, the average acquisition time for acceptable image quality in the validation cohort was 2.99 ± 0.91 min, ranging from 2.18 to 6.35 min, which was reduced by 36.50% ~ 78.20% compared with the fixed acquisition time of 10 min. Subjective evaluation showed that acceptable image quality could be obtained at 3.00 min in the validation group, with an average subjective score of 3.44 ± 0.53 (kappa = 0.97, 95% CI: 0.96 ~ 0.98). Bland-Altman analysis revealed good agreement between the proposed regimen and the fixed acquisition time cohort.
A patient-specific acquisition time regimen was proposed in NET patients in development cohort and validated its feasibility in patients with NETs in validation cohort by Ga-DOTATATE total-body PET/CT imaging. Based on the proposed regimen, the homogenous image quality with optimal acquisition time was available independent of body mass.
示踪剂的注射活动、采集时间、患者特有的光子衰减和较大的体重会影响图像质量。在临床实践中，固定的采集时间和与体重相关的示踪剂注射活动会导致图像质量的巨大差异。因此，本研究提出了一种针对 Ga-DOTATATE 全身正电子发射断层扫描-计算机断层扫描（PET/CT）的患者特异性采集时间方案，以抵消体重（kg）对图像质量的影响，并为神经内分泌肿瘤（NETs）患者获得可接受且一致的图像。
由 19 名连续接受全活性（88.7-204.9 MBq，2.0 ± 0.1 MBq/kg）的患者组成的开发队列用于建立采集时间方案。肝 SNR（信噪比，SNR）通过注射活性（MBq）和采集时间（min）的乘积进行归一化（SNR）。进行 SNR 与体重（BM，kg）的线性相关性拟合。使用 5 分制李克特量表进行图像质量的主观评估，以确定可接受 SNR 的阈值，并基于 BM 提出优化的采集方案，然后通过 57 名连续 NET 患者的验证队列进行验证，这些患者接受半活性（66.9 ± 11.3 MBq，1.0 ± 0.1 MBq/kg）和固定采集时间方案。
SNR 与 BM（kg）之间的线性相关性（R=0.63）为 SNR=-0.01BM+1.50。可接受图像质量的阈值 SNR 为 11.2。患者特异性可变采集时间方案确定为：t（min）=125.4/（注射活性）（-0.01*BM+1.50）。基于该方案，验证队列中获得可接受图像质量的平均采集时间为 2.99±0.91 min，范围为 2.18-6.35 min，与固定的 10 min 采集时间相比，减少了 36.50%78.20%。主观评估显示，验证组在 3.00 min 时可获得可接受的图像质量，平均主观评分为 3.44±0.53（kappa=0.97，95%CI：0.960.98）。Bland-Altman 分析表明，该方案与固定采集时间队列之间具有良好的一致性。
通过 Ga-DOTATATE 全身 PET/CT 成像，在开发队列中提出了针对 NET 患者的患者特异性采集时间方案，并在 NET 患者的验证队列中验证了其可行性。基于该方案，可获得与体重无关的同质图像质量和最佳采集时间。
