Nuclear Medicine Department, University Hospital, Caen, France.
Dermatology Department, University Hospital, Caen, France.
Ann Nucl Med. 2021 Jun;35(6):669-679. doi: 10.1007/s12149-021-01608-5. Epub 2021 Mar 26.
To evaluate the use of digital F-FDG PET/CT with small-voxels reconstruction for detecting in-transit metastases in melanoma patients with primary lesion located on the upper or lower limbs, in comparison with standard reconstruction and European Association of Nuclear Medicine Research limited (EARL)-compliant reconstruction mimicking former generation PET systems.
Forty-six PET examinations acquired in list mode on a Vereos digital PET/CT system were reconstructed with (1) the standard reconstruction [2 iterations, 10 subsets (2i10s), point-spread function (PSF) modelling and time-of-flight enabled, no post-filtering and voxel size of 2 mm], (2) a small-voxel reconstruction using 1 mm voxels otherwise using the same parameters, (3) an EARL-compliant reconstruction mimicking a former generation system. Comparison of results across these reconstructions was made for a blind randomized review using a 3-point scale for the presence of in-transit metastases and image quality as well as for tumour-to-background (T/B) ratios and noise level in reference organs.
Seven of the thirty-two EARL-compliant images classified as negative moved to positive on 1mm images, and 5 of the 6 EARL-compliant images classified as indeterminate moved to positive on 1mm images (P = 0.01). Amongst a total of 20 PET examinations classified as positive using the 1mm reconstruction, fifteen were considered true positive, five false positive results occurred. Twenty-four patients with 1 mm PSF images were classified as negative, none of those under active surveillance experienced in-transit metastases during the 17 months following their PET examination. The positive likelihood ratio for the 1 mm reconstruction was much higher than that observed for EARL-compliant images (14.7 vs 7.82). Importantly, negative likelihood ratios for the 1 mm and 1mm reconstruction were almost perfect. Compared to EARL-compliant data, T/B ratios extracted from the 1mm showed a 2.84-fold increase (P < 0.001). A similar pattern of statistically significant increase was observed for noise level in organs of reference. Image quality for the torso was found to be significantly lower for 1mm reconstruction (P = 0.03). Image quality for the limbs was found to be better for 1mm (P < 0.001).
Digital PET with small-voxel reconstruction brings an additional value for the detection of in-transit metastases by reducing the number of indeterminate findings and making up for falsely negative scans using former generation PET systems. An acquisition encompassing lower or upper limbs as appropriate should be performed.
评估使用小体素重建的数字 F-FDG PET/CT 检测位于上肢或下肢的原发性黑素瘤患者的经皮转移，与标准重建和符合欧洲核医学研究协会（EARL）的前一代 PET 系统模拟的符合 EARL 标准的重建进行比较。
在 Vereos 数字 PET/CT 系统上以列表模式采集 46 次 PET 检查，分别使用（1）标准重建[2 次迭代，10 个子集（2i10s），点扩散函数（PSF）建模和启用飞行时间，无后滤波，体素大小为 2mm]、（2）使用 1mm 体素的小体素重建，其他参数相同，（3）符合 EARL 标准的重建，模拟前一代系统。通过盲法随机审查，使用 3 分制对存在经皮转移和图像质量以及参考器官中的肿瘤与背景（T/B）比值和噪声水平进行比较。
32 个符合 EARL 标准的图像中，有 7 个被归类为阴性的图像在 1mm 图像上变为阳性，6 个符合 EARL 标准的图像中有 5 个被归类为不确定的图像在 1mm 图像上变为阳性（P=0.01）。在总共 20 次使用 1mm 重建被归类为阳性的 PET 检查中，有 15 次被认为是真正的阳性，有 5 次出现假阳性结果。24 例接受 1mm PSF 图像检查的患者被归类为阴性，在 PET 检查后的 17 个月内，没有任何接受主动监测的患者发生经皮转移。1mm 重建的阳性似然比远高于符合 EARL 标准的图像（14.7 比 7.82）。重要的是，1mm 和 1mm 重建的阴性似然比几乎是完美的。与 EARL 符合数据相比，从 1mm 提取的 T/B 比值增加了 2.84 倍（P<0.001）。在参考器官中的噪声水平也观察到了类似的统计学显著增加模式。1mm 重建的躯干图像质量明显较低（P=0.03）。1mm 重建的四肢图像质量更好（P<0.001）。
数字 PET 采用小体素重建，通过减少不确定发现的数量，并弥补使用前一代 PET 系统的假阴性扫描，为检测经皮转移提供了附加价值。应根据情况采集包含下肢或上肢的扫描。
