SUV小于2.5的孤立性肺结节18F - FDGPET/CT诊断价值初探

摘要

目的 正电子断层显像(PET)通常以标准摄取值(SUV)≥2.5为肺癌诊断标准,但仍有部分SUV＜ 2.5的孤立性肺结节( SPN＜2.5)为肺癌.本研究旨在分析SPN＜25氟代脱氧葡萄糖(18F- FDG) PET/CT表现及其诊断价值.方法 51例18F-FDG PET/CT早期显像SUV平均值(SUVavg)＜ 2.5的孤立性肺结节病人纳入研究.对SPN放射性摄取测量采用两种方法:视觉分析及半定量分析.测量SPN的早期及延迟显像的SUVavg、SUVmax及其早期-延迟变化率(△SUVavg、△SUVmax).37例以病理诊断及14例以2年以上临床随诊结果 为最终诊断标准.统计学分析采用SPSS 16.0软件.结果 51例SPN＜25患者中,良性11例,恶性40例.虽然良恶性SPN＜25患者各项SUV值间均无统计学差异(P＞0.05),但恶性SPN＜25患者各项SUV值均有高于良性的趋势,特别是△SUVavg、△SUVmax.以△SUVmax＞0为诊断阈值,18F- FDG PET/CT诊断恶性SPN的敏感性68.4％、特异性60.0％、准确性66.7％、阳性预测值86.7％及阴性预测值33.3％.视觉分析:无FDG摄取的SPN＜2.59例中,5例为良性,4例为恶性；有FDG摄取的SPN＜2.542例中,6例良性,36例恶性,两组之间有显著的统计学差异,P＝0.02.良恶性SPN＜2.5的CT密度及大小之间均无统计学差异(P＞0.05).综合PET和CT信息分析SPN＜2.5,18F- FDG PET/CT诊断恶性SPN＜2.5的敏感性97.5％、特异性54.5％、准确性88.2％、阳性预测值88.6％、阴性预测值85.7％.结论 单纯以SUV≥2.5为标准鉴别诊断SPN会导致肺癌的漏诊.对于此类结节,△SUV有较高的肺癌阳性预测值；FDG摄取视觉分析能提高结节的良恶性鉴别准确率；综合FDG PET和CT分析的PET/CT能显著提高诊断肺癌的敏感性和准确性,但特异性较低.%Objective Traditionly,a FDC standardized uptake value (SUV) of 2.5 is used as a cutoff of pulmonary malignancies. However,the frequency of malignancies with an SUV of <2. 5 is significant,and this study aimed to evaluate the value of "F - FDG PET/ CT for diagnosis of solitary pulmonary nodules ( SPNs) with 18F - FDG uptake below the initial average standardized uptake value ( SU-Vavg) of 2. 5. Methods We retrospectively analyzed 51 patients who had SPNs with an initial SUVavg of < 2. 5. The uptake of 18F -FDG was graded by semiquantitative methods ( SUVavg, SUVmax, △ SUVavg,△ASUVmax) and a visual method. Besides above, we analyzed the density and size of SPNs. Final classification was based on histopathologic findings or at least 24 months of clinical follow - up. Results We found 40 malignant and 11 benign lesions. Though there were no significant differences between SUV( including all the SUVs and △ SUV) of benign and malignant SPNs, there was a tendency that SUV of malignant SPNs was higher than that of benign ones( especially △ SUV) . When a cutoff of △SUVmax above 0 was used, the sensitivity, specificity, accuracy, positive and negative predictive values of 18F FDG PET/CT in diagnosis SPN were 68.4% ,60.0% , 66. 7% ,86. 7% ,33. 3% .respectively. There were 5 benign SPNs and 4 malignant SPNs in total 9 absent FDG uptake SPNs. There were 6 benign SPNs and 36 malignant SPNs in total 42 visually evident FDG uptake SPNs (P =0.02). There was no significant difference between benign and malignant SPNs in CT density and diameter (P =0. 71, 0. 24). The sensitivity, specificity, accuracy, the positive and negative predictive values of 18 F - FDG PET/CT in diagnosis SPNs were 97.5% ,54.5% ,88.2% ,88.6% ,85.7% .respectively. Conclusion These results suggested that SPNs with low 18F - FDG uptake,SUVavg and SUVmax did not improve the accuracy of 18F - FDG PET /CT. A SUV might be helpful in differential diagnosis. Visual analysis was more valuable than semiquantitative analysis. 18F -FDG PET/CT demonstrates an excellent performance in classifying SPNs with an SUVavg of <2.5 as benign or malignant with a highly sensitivity and accuracy,though the specificity was low.