PET/CT图像膈肌上方条带状伪影特征及影响因素分析

Stripped Artifact in PET/CT Imaging:Characteristics and Contributing Factors

目的在PET/CT扫描中,PET图像膈肌上方、下肺区域条带状放射性减低或缺损这一伪影(S伪影)较为常见。本研究分析S伪影发生率、特征、影响因素。方法于笔者医院行PET/CT检查的100例患者纳入研究,分析S伪影发生率及影响因素。结果 S伪影总体发生率为46%。S伪影分布特征:男性S伪影发生率58.3%,女性27.5%,P<0.05;左侧S伪影发生率为42%,右侧为21%,P<0.05。S伪影对肺SUV值的影响:伪影处肺组织SUVmax和SUVmean(分别为0.281±0.196和0.200±0.166)明显低于无伪影处肺组织(分别为0.622±0.171和0.500±0.140,P<0.05)。影响S伪影发生率的因素:膈顶部PET与CT空间配准良好者S伪影出现率为25.7%,配准不良者为34.6%;同机CT冠状面无膈顶部阶梯状伪影者S伪影发生率为28.6%,有阶梯伪影者为38.3%。同时发生上述两种情况者S伪影的发生率为43.6%,高于只发生匹配不良者(30.8%)或阶梯状伪影者(28.6%)。两种情况皆不发生者S伪影的发生率仍高达24.5%。结论 PET/CT图像中膈肌上方条带状伪影常见;男性发生率更高,左侧更多见;伪影导致显著低估下肺部SUV;PET与CT图像配准程度及CT膈肌阶梯状伪影与条带状伪影部分相关。

Objective The stripped artifact （S artifact） which appeares as the stripped cold areas at the interface of the lungs and diaphragm is usually seen in PET/CT imaging. The aim of this study is to analyze its frequency, characteristics and contributing factors. Methods One hundred PET/CT scans were included, whose frequency, characteristics and contributing factors of S artifact were ana- lyzed. Results The total frequency of S artifact was 46%. Distribution characteristics： the frequencies of S artifact in male and in female patients were 58.3% and 27.5% , respectively, with significant difference （ P 〈 0.05 ） ; those on the left and right side were 42% and 21% , respectively, with significant difference （ P 〈 0.05 ）. The impact on SUV ： the maximum value of SUV （ SUVo~ ） （0.281 ＋ 0. 196） and the mean value of SUV （SUV ） （0. 200 ＋ 0. 166） in the S artifact areas were significantly lower than those in the no artifact areas （ SUVz^x O. 622 ~ 0.171 , SUV 0. 500 ＋ O. 140, respectively, P 〈 0.05 ）. The contributing factors of S artifact ： the frequencies of S arti- fact in patients with the diaphragmatic dome alignment and misalignmet between the PET and CT image were 25.7% and 34.6% , respec- tively; those in patients with or without the echelon artifact of the diaphragm were 38.3% and 28.6%. The frequency of S artifact in pa- tients with both above conditions was 43.6% , higher than that in patients with misalignment alone （30.8%） and echelon artifact alone （28.6%）. However, in patients without any above condition, the frequency of S artifact was still 24.5%. Conclusion The stripped ar- tifact can be usually seen in PET/CT images and is more common in male patients and on the left side. S artifact leads to a significant de- creased SUV in the lower lungs, and is partially due to the alignment between PET and CT images and the echelon artifact of the dia- phragm.