Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, 54 Shogoinkawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan.
Department of Radiology, Shiga General Hospital, Shiga, Japan.
AJR Am J Roentgenol. 2021 Feb;216(2):486-493. doi: 10.2214/AJR.19.22245. Epub 2020 Nov 25.
Flexible PET (fxPET) was designed to fit existing MRI systems. The newly modified nonlocal means (NLM) algorithm is combined with the 3D dynamic row-action maximum likelihood algorithm (DRAMA). We investigated qualitative and quantitative acceptability of fxPET images reconstructed by modified NLM compared with whole-body (WB) PET/CT images and conventional 3D DRAMA reconstruction alone. Fifty-nine patients with known or suspected malignancies underwent WB PET/CT scanning approximately 1 hour after the injection of F-FDG, after which they underwent fxPET scanning. Two readers rated the quality of fxPET images by consensus. Detection rate (the proportion of lesions found on PET), maximal standardized uptake value (SUV), metabolic tumor volume (MTV), total lesion glycolysis (TLG), tumor-to-normal liver ratio (TNR), and background liver signal-to-noise ratio (SNR) were compared among the three datasets. Higher image quality was obtained by modified NLM reconstruction than by conventional reconstruction without statistical significance. The detection rate was comparable among three datasets. SUV was significantly higher, and MTV and TLG were significantly lower in the modified NLM dataset ( < 0.002) than in the other two datasets, with significantly positive correlations ( < 0.001; Spearman rank correlation coefficient, 0.87-0.99). The TNRs in modified NLM images were significantly larger than in the other datasets ( < 0.05). The background SNRs in modified NLM images were comparable with those in WB PET/CT images, and significantly higher than in the conventional fxPET images ( < 0.005). The modified NLM algorithm was clinically acceptable, yielding higher TNR and background SNR compared with conventional reconstruction. Image quality and the lesion detection rate were comparable in this population.
灵活 PET（fxPET）旨在与现有的 MRI 系统相匹配。新修改的非局部均值（NLM）算法与 3D 动态行动作似然算法（DRAMA）相结合。我们研究了通过修改的 NLM 重建的 fxPET 图像与全身（WB）PET/CT 图像以及单独的传统 3D 重建的 DRAMA 相比的定性和定量可接受性。59 名已知或疑似恶性肿瘤的患者在注射 F-FDG 后约 1 小时进行 WB PET/CT 扫描，然后进行 fxPET 扫描。两名读者通过共识对 fxPET 图像的质量进行评分。比较了三个数据集之间的检出率（在 PET 上发现的病变比例）、最大标准化摄取值（SUV）、代谢肿瘤体积（MTV）、总肿瘤糖酵解（TLG）、肿瘤与正常肝脏比值（TNR）和背景肝脏信噪比（SNR）。与传统重建相比，修改后的 NLM 重建可获得更高的图像质量，但无统计学意义。三个数据集之间的检出率相当。与其他两个数据集相比，修改后的 NLM 数据集的 SUV 显著更高，MTV 和 TLG 显著更低（<0.002），并且具有显著的正相关关系（<0.001；Spearman 秩相关系数，0.87-0.99）。在修改后的 NLM 图像中，TNR 显著大于其他数据集（<0.05）。修改后的 NLM 图像的背景 SNR 与 WB PET/CT 图像相当，并且显著高于传统的 fxPET 图像（<0.005）。修改后的 NLM 算法在临床上是可以接受的，与传统重建相比，它可以获得更高的 TNR 和背景 SNR。在该人群中，图像质量和病变检出率相当。
