Department of Nuclear Medicine, West German Cancer Center (WTZ), University Hospital Essen, University of Duisburg-Essen, Essen, Germany; German Cancer Consortium (DKTK), Partner Site University Hospital Essen, Essen, Germany.
Department of Nuclear Medicine, West German Cancer Center (WTZ), University Hospital Essen, University of Duisburg-Essen, Essen, Germany; German Cancer Consortium (DKTK), Partner Site University Hospital Essen, Essen, Germany.
Phys Med. 2023 Oct;114:103149. doi: 10.1016/j.ejmp.2023.103149. Epub 2023 Sep 30.
The aim of this study was to investigate conditions for reliable quantification of sub-centimeter lesions with lowF,Ga, andI uptake using a silicon photomultiplier-based PET/CT system.
A small tumor phantom was investigated under challenging but clinically realistic conditions resembling prostate and thyroid cancer lymph node metastases (6 spheres with 3.7-9.7 mm in diameter, 9 different activity concentrations ranging from about 0.25-25 kBq/mL, and a signal-to-background ratio of 20). Radionuclides with different positron branching ratios and prompt gamma coincidence contributions were investigated. Maximum-, contour-, and oversize-based partial volume effect (PVE) correction approaches were applied. Detection and quantification performance were estimated, considering a ±30 % deviation between imaged-derived and true activity concentrations as acceptable. A standard and a prolonged acquisition time and two image reconstruction algorithms (time-of-flight with/without point spread function modelling) were analyzed. Clinical data were evaluated to assess agreement of PVE-correction approaches indicating lesion quantification validity.
The smallest 3.7-mm sphere was not visible. If the lesions were clearly observed, quantification was, except for a few cases, acceptable using contour- or oversized-based PVE-corrections. Quantification accuracy did not substantially differ between F, Ga, and I. No systematic differences between the analyzed reconstruction algorithms or shorter and larger acquisition times were observed. In the clinical evaluation of 20 lesions, an excellent statistical agreement between oversize- and contour-based PVE-corrections was observed.
At the lower end of size (<10 mm) and activity concentration ranges of lymph-node metastases, quantification with reasonable accuracy is possible for F, Ga, and I, possibly allowing pre-therapeutic lesion dosimetry and individualized radionuclide therapy planning.
本研究旨在探讨使用基于硅光电倍增管的 PET/CT 系统可靠量化低 F、Ga 和 I 摄取的亚厘米级病变的条件。
在类似于前列腺和甲状腺癌淋巴结转移的具有挑战性但临床现实的条件下研究小肿瘤体模（6 个直径为 3.7-9.7 毫米的球体，9 种不同的活性浓度范围约为 0.25-25kBq/mL，信噪比为 20）。研究了具有不同正电子分支比和瞬发伽马符合贡献的放射性核素。应用最大、轮廓和超大型基于部分容积效应（PVE）校正方法。考虑到图像衍生的和真实的活性浓度之间的偏差±30%可接受，估计了检测和定量性能。分析了标准和延长的采集时间以及两种图像重建算法（具有/不具有点扩散函数建模的飞行时间）。评估临床数据以评估指示病变定量有效性的 PVE 校正方法的一致性。
最小的 3.7 毫米球体不可见。如果病变清晰可见，除了少数情况下，使用轮廓或超大基于 PVE 校正的定量是可以接受的。定量准确性在 F、Ga 和 I 之间没有显著差异。未观察到分析的重建算法之间或较短和较长采集时间之间存在系统差异。在 20 个病变的临床评估中，观察到超大基于和轮廓基于 PVE 校正之间具有极好的统计学一致性。
在淋巴结转移的大小（<10 毫米）和活性浓度范围的低端，F、Ga 和 I 的定量具有合理的准确性是可能的，可能允许进行治疗前病变剂量测定和个体化放射性核素治疗计划。
