Nuclear Medicine, IRCCS, Azienda Ospedaliero-Universitaria Di Bologna, Bologna, Italy.
Nuclear Medicine, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna, Italy.
Eur J Nucl Med Mol Imaging. 2022 Apr;49(5):1607-1612. doi: 10.1007/s00259-021-05592-w. Epub 2021 Oct 25.
AIM/INTRODUCTION: Digital PET/CT allows Q.Clear image reconstruction with different Beta (β) levels. However, no definitive standard β level for [68 Ga]Ga-DOTANOC PET/CT has been established yet. As patient's body mass index (BMI) can affect image quality, the aim of the study was to visually and semi-quantitatively assess different β levels compared to standard OSEM in overweight patients.
Inclusion criteria: (1) patients with NEN included in a prospective CE-approved electronic archive; (2) [68 Ga]Ga-DOTANOC PET/CT performed on a digital tomograph between September2019/March2021; (3) BMI ≥ 25. Images were acquired following EANM guidelines and reconstructed with OSEM and Q.Clear with three β levels (800, 1000, 1600). Scans were independently reviewed by three expert readers, unaware of clinical data, who independently chose the preferred β level reconstruction for visual overall image quality. Semi-quantitative analysis was performed on each scan: SUVmax of the highest uptake lesion (SUVmax-T), liver background SUVmean (SUVmean-L), SUVmax-T/SUVmean-L, Signal-to-noise ratio for both liver (LSNR) and the highest uptake lesion (SNR-T), Contrast-to-noise ratio (CNR).
Overall, 75 patients (median age: 63 years old [23-87]) were included: pre-obesity sub-group (25 ≤ BMI < 30, n = 50) and obesity sub-group (BMI ≥ 30, n = 25). PET/CT was positive for disease in 45/75 (60.0%) cases (14 obese and 31 pre-obese patients). Agreement among readers' visual rating was high (Fleiss κ = 0.88) and the β1600 was preferred in most cases (in 96% of obese patients and in 53.3% of pre-obese cases). OSEM was considered visually equal to β1600 in 44.7% of pre-obese cases and in 4% of obese patients. In a minority of pre-obese cases, OSEM was preferred (2%). In the whole population, CNR, SNR-T and LSNR were significantly different (p < 0.001) between OSEM and β1600, conversely to SUVmean-L (not significant). These results were also confirmed when calculated separately for the pre-obesity and obesity sub-groups β800 and β1000 were always rated inferior.
Q.Clear is a new technology for PET/CT image reconstruction that can be used to increase CNR and SNR-T, to subsequently optimise overall image quality as compared to standard OSEM. Our preliminary data on [68 Ga]Ga-DOTANOC PET/CT demonstrate that in overweight NEN patients, β1600 is preferable over β800 and β1000. Further studies are warranted to validate these results in lesions of different anatomical region and size; moreover, currently employed interpretative PET positivity criteria should be adjusted to the new reconstruction method.
目的/引言：数字 PET/CT 允许使用不同的β水平进行 Q.Clear 图像重建。然而，目前尚未为[68Ga]Ga-DOTANOC PET/CT 确定明确的标准β水平。由于患者的体重指数（BMI）可能会影响图像质量，因此本研究的目的是在超重患者中，通过视觉和半定量评估与标准 OSEM 相比的不同β水平。
纳入标准：（1）前瞻性 CE 批准的电子档案中包含的神经内分泌肿瘤（NEN）患者；（2）2019 年 9 月至 2021 年 3 月期间在数字断层扫描仪上进行[68Ga]Ga-DOTANOC PET/CT；（3）BMI≥25。图像按照 EANM 指南采集，并使用 OSEM 和 Q.Clear 进行重建，β水平分别为 800、1000 和 1600。三位经验丰富的读者独立审查扫描，不了解临床数据，他们独立选择首选的β水平重建以获得整体视觉图像质量。对每个扫描进行半定量分析：摄取最高的病变的 SUVmax（SUVmax-T）、肝脏背景 SUVmean（SUVmean-L）、SUVmax-T/SUVmean-L、肝脏的信噪比（LSNR）和摄取最高的病变的 SNR-T（SNR-T）、对比噪声比（CNR）。
总体而言，共纳入 75 名患者（中位年龄：63 岁[23-87]）：预肥胖亚组（25≤BMI<30，n=50）和肥胖亚组（BMI≥30，n=25）。75 例患者中有 45 例（60.0%）（14 例肥胖患者和 31 例预肥胖患者）的 PET/CT 检查为阳性。读者视觉评分的一致性很高（Fleiss κ=0.88），β1600 在大多数情况下都更受欢迎（肥胖患者中有 96%，预肥胖患者中有 53.3%）。在 44.7%的预肥胖病例和 4%的肥胖病例中，OSEM 被认为与β1600 视觉相等。在少数预肥胖病例中，OSEM 更受欢迎（2%）。在整个人群中，OSEM 和β1600 之间 CNR、SNR-T 和 LSNR 差异具有统计学意义（p<0.001），而 SUVmean-L 则没有统计学意义（p>0.05）。当分别为预肥胖亚组和肥胖亚组计算β800 和β1000 时，也证实了这些结果，β800 和β1000 始终被评为较差。
Q.Clear 是一种新的 PET/CT 图像重建技术，与标准 OSEM 相比，它可以增加 CNR 和 SNR-T，从而优化整体图像质量。我们在[68Ga]Ga-DOTANOC PET/CT 上的初步数据表明，在超重的神经内分泌肿瘤患者中，β1600 优于β800 和β1000。需要进一步的研究来验证这些结果在不同解剖区域和大小的病变中的适用性；此外，目前使用的 PET 阳性解读标准应适应新的重建方法。
