UNLABELLED:In the diagnosis of giant cell arteritis (GCA) with aortic involvement, (18)F-FDG PET has been demonstrated to be a powerful tool. No other imaging method is able to directly detect acute inflammation within the aortic wall. However, because GCA is a rare PET indication, the assessment of GCA with (18)F-FDG PET remains difficult and highly dependent on the experience of the investigator. This study aimed to semiquantify the relationship between aortic and liver uptake and to introduce a receiver operating characteristic (ROC)-based cutoff ratio to allow investigator- and experience-independent GCA diagnosis with optimal sensitivity and specificity. Ratios of aortic wall uptake versus liver uptake were calculated in a group of GCA patients and a control group. These data were assessed in an ROC analysis, and finally, a cutoff-ratio-optimizing strategy was applied. METHODS:Twenty-three patients with initially suspected GCA (18 positive for GCA criteria, 5 negative) and 36 matched controls were included. The control subjects underwent PET for oncologic diagnostics. None had intrathoracic or hepatic disease or therapy-related tracer accumulation. Additionally, physiologic liver metabolism was ensured by the presence of normal liver enzymes. After defining regions of interest over the thoracic aorta and the liver, we calculated maximal standardized uptake value ratios. Sensitivities and specificities for cutoff ratios from 0.1 to 2.5 were estimated and were ultimately used to assess an optimal cutoff ratio for separating GCA patients from controls. To further investigate the usefulness of the resulting cutoff ratio, we tested it in a second control group with changed hepatic metabolism and elevated liver enzymes. RESULTS:ROC analysis revealed optimal selectivity for a cutoff ratio of 1.0. This ratio led to a sensitivity of 88.9%, a specificity of 95.1%, and an accuracy of 94.4%. When this aorta-to-liver ratio was applied to the control group with pathologic liver metabolism, the resulting specificity was 95.6%. CONCLUSION:The (18)F-FDG PET region-of-interest analysis with aorta-to-liver maximal standardized uptake value ratios is a reliable, investigator-independent indicator of GCA not affected by minor inflammation-associated changes in hepatic metabolism. Our results for a cutoff ratio of 1.0 prove that (18)F-FDG PET is a method of high sensitivity and specificity for GCA-related large-vessel inflammation.

译文

引爆标签:在诊断主动脉受累的巨细胞动脉炎(GCA)中,已证明(18)F-FDG PET是一种强大的工具。没有其他成像方法能够直接检测主动脉壁内的急性炎症。但是,由于GCA是一种罕见的PET适应症,因此用(18)F-FDG PET进行GCA评估仍然很困难,并且高度依赖于研究者的经验。这项研究旨在半定量主动脉和肝脏摄取之间的关系,并引入基于受体工作特征(ROC)的截留比,以使研究者和经验独立的GCA诊断具有最佳的敏感性和特异性。计算了一组GCA患者和对照组的主动脉壁摄取与肝脏摄取的比率。这些数据在ROC分析中进行了评估,最后,采用了截止比例优化策略。
方法:包括23例最初怀疑为GCA的患者(GCA标准为18例阳性,5例阴性)和36例匹配的对照组。对照组接受PET进行肿瘤诊断。没有人有胸内或肝病或与治疗有关的示踪剂蓄积。另外,正常肝酶的存在确保了生理肝的新陈代谢。在定义了胸主动脉和肝脏的目标区域后,我们计算了最大标准化摄取值比率。估计了截留比从0.1到2.5的敏感性和特异性,并最终用于评估将GCA患者与对照组分开的最佳截留比。为了进一步研究所得截留比的有用性,我们在肝代谢改变和肝酶升高的第二个对照组中进行了测试。
结果:ROC分析显示最佳的选择性为1.0的截止值。该比率导致灵敏度为88.9%,特异性为95.1%和准确度为94.4%。当将该主动脉与肝脏的比率应用于具有病理性肝代谢的对照组时,所产生的特异性为95.6%。
结论:(18)F-FDG PET感兴趣的区域分析具有主动脉-肝脏最大标准化摄取值比是一种可靠的,独立于研究者的指示性GCA指标,不受肝脏炎症相关的微小变化影响。我们的截留比为1.0的结果证明(18)F-FDG PET是一种针对GCA相关的大血管炎症的高灵敏度和特异性方法。

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