评估使用 PET/CT 进行常规 Y-90 成像的采集方案。
Assessment of acquisition protocols for routine imaging of Y-90 using PET/CT.
机构信息
Nuclear Medicine Department, University Hospital of Nantes, Place Alexis Ricordeau, Nantes, 44093, France.
出版信息
EJNMMI Res. 2013 Feb 17;3(1):11. doi: 10.1186/2191-219X-3-11.
BACKGROUND
Despite the early theoretical prediction of the 0+-0+ transition of 90Zr, 90Y-PET underwent only recently a growing interest for the development of imaging radioembolization of liver tumors. The aim of this work was to determine the minimum detectable activity (MDA) of 90Y by PET imaging and the impact of time-of-flight (TOF) reconstruction on detectability and quantitative accuracy according to the lesion size.
METHODS
The study was conducted using a Siemens Biograph® mCT with a 22 cm large axial field of view. An IEC torso-shaped phantom containing five coplanar spheres was uniformly filled to achieve sphere-to-background ratios of 40:1. The phantom was imaged nine times in 14 days over 30 min. Sinograms were reconstructed with and without TOF information. A contrast-to-noise ratio (CNR) index was calculated using the Rose criterion, taking partial volume effects into account. The impact of reconstruction parameters on quantification accuracy, detectability, and spatial localization of the signal was investigated. Finally, six patients with hepatocellular carcinoma and four patients included in different 90Y-based radioimmunotherapy protocols were enrolled for the evaluation of the imaging parameters in a clinical situation.
RESULTS
The highest CNR was achieved with one iteration for both TOF and non-TOF reconstructions. The MDA, however, was found to be lower with TOF than with non-TOF reconstruction. There was no gain by adding TOF information in terms of CNR for concentrations higher than 2 to 3 MBq mL-1, except for infra-centimetric lesions. Recovered activity was highly underestimated when a single iteration or non-TOF reconstruction was used (10% to 150% less depending on the lesion size). The MDA was estimated at 1 MBq mL-1 for a TOF reconstruction and infra-centimetric lesions. Images from patients treated with microspheres were clinically relevant, unlike those of patients who received systemic injections of 90Y.
CONCLUSIONS
Only one iteration and TOF were necessary to achieve an MDA around 1 MBq mL-1 and the most accurate localization of lesions. For precise quantification, at least three iterations gave the best performance, using TOF reconstruction and keeping an MDA of roughly 1 MBq mL-1. One and three iterations were mandatory to prevent false positive results for quantitative analysis of clinical data.
TRIAL REGISTRATION
http://IDRCB 2011-A00043-38 P101103.
背景
尽管早在理论上就预测了 90Zr 的 0+-0+ 跃迁，但 90Y-PET 直到最近才因其对肝脏肿瘤放射性栓塞成像的发展而受到越来越多的关注。本研究的目的是确定 90Y 通过 PET 成像的最小可检测活性 (MDA)，并根据病变大小，评估飞行时间 (TOF) 重建对检测能力和定量准确性的影响。
方法
本研究使用配备 22cm 大轴向视野的西门子 Biograph mCT 进行。IEC 体模的躯干形状，包含五个共面球体，球体被均匀填充，实现了 40:1 的球体与背景的比值。在 14 天内，使用 30 分钟进行了 9 次成像。使用和不使用 TOF 信息对正电子发射断层扫描（PET）进行了重建。使用 Rose 标准计算了对比噪声比 (CNR) 指数，同时考虑了部分容积效应。研究了重建参数对定量准确性、检测能力和信号空间定位的影响。最后，纳入了 6 名肝细胞癌患者和 4 名接受不同 90Y 放射性免疫治疗方案的患者，评估了临床情况下的成像参数。
结果
对于 TOF 和非 TOF 重建，都使用一次迭代获得了最高的 CNR。然而，与非 TOF 重建相比，使用 TOF 重建时 MDA 较低。对于浓度高于 2 至 3MBq·mL-1 的情况，除了亚厘米级的病变外，添加 TOF 信息并不能提高 CNR。对于单次迭代或非 TOF 重建，计算出的放射性活度高度低估（取决于病变大小，减少 10% 至 150%）。TOF 重建和亚厘米级病变的 MDA 估计值为 1MBq·mL-1。接受微球治疗的患者的图像具有临床相关性，而接受 90Y 全身注射的患者的图像则没有。
结论
仅需一次迭代和 TOF 即可实现约 1MBq·mL-1 的 MDA 和病变的最准确定位。为了进行精确的定量分析，至少需要三次迭代，同时使用 TOF 重建并保持大约 1MBq·mL-1 的 MDA。对于定量分析临床数据，需要进行一次和三次迭代以防止假阳性结果。
试验注册
http://IDRCB 2011-A00043-38 P101103。
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