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.

Materials and methods

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).

Results

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.

Conclusions

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.

中文翻译：

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Q.Clear 重建可用于改善超重 NEN 患者的 [68 Ga]Ga-DOTANOC PET/CT 图像质量吗？

目标/介绍

数字 PET/CT 允许使用不同的 Beta (β) 水平重建 Q.Clear 图像。然而，尚未建立 [68 Ga]Ga-DOTANOC PET/CT 的明确标准 β 水平。由于患者的体重指数 (BMI) 会影响图像质量，因此该研究的目的是通过视觉和半定量的方式评估超重患者与标准 OSEM 相比的不同 β 水平。

材料和方法

纳入标准：（1）NEN 患者纳入前瞻性 CE 批准的电子档案；(2) [68 Ga]Ga-DOTANOC PET/CT 在 2019 年 9 月/2021 年 3 月期间在数字断层扫描仪上进行；(3) BMI ≥ 25。按照 EANM 指南获取图像，并使用 OSEM 和 Q.Clear 重建三个 β 水平（800、1000、1600）。扫描由三位专家读者独立审查，不了解临床数据，他们独立选择首选的 β 水平重建以获得视觉整体图像质量。对每次扫描进行半定量分析：最高摄取病变的 SUVmax (SUVmax-T)、肝脏背景 SUVmean (SUVmean-L)、SUVmax-T/SUVmean-L、双肝信噪比 (LSNR) ) 和最高摄取病变 (SNR-T)、对比度噪声比 (CNR)。

结果

总体而言，包括 75 名患者（中位年龄：63 岁 [23-87]）：肥胖前亚组（25 ≤ BMI < 30，n = 50）和肥胖亚组（BMI ≥ 30，n = 25 ）。PET/CT 在 45/75 (60.0%) 例（14 名肥胖患者和 31 名肥胖前患者）中呈阳性。读者视觉评分的一致性很高（Fleiss κ = 0.88），大多数情况下首选 β1600（96% 的肥胖患者和 53.3% 的肥胖前病例）。在 44.7% 的肥胖前病例和 4% 的肥胖患者中，OSEM 被认为在视觉上等于 β1600。在少数肥胖前病例中，首选 OSEM (2%)。在整个人群中，CNR、SNR-T 和 LSNR 在 OSEM 和 β1600 之间存在显着差异（p < 0.001），与 SUVmean-L 相反（不显着）。

结论

Q.Clear 是一种用于 PET/CT 图像重建的新技术，可用于提高 CNR 和 SNR-T，从而与标准 OSEM 相比随后优化整体图像质量。我们关于 [68 Ga]Ga-DOTANOC PET/CT 的初步数据表明，在超重 NEN 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；此外，目前采用的解释性 PET 阳性标准应根据新的重建方法进行调整。