Objective To investigate the diagnoses value of dual-phase 18 F-FDG PET/CT in malignant tumors. Methods 102 patients with malignant tumors and 29 patients with benign lesiongs underwent dual-phase 18 F-FDG PET/CT images. The final diagnoses of these patients were proved by histopathology or by follow-up. The imaging protocol included a whole body PET/CT at 40 minutes and a local PET/CT at 2 hours post-injection. The maximum standardized uptake value( SUVmax) was gotten at these both time points. The retention index(RI)was calculated. Results A cutoff of 20% change for SUVmax over time showed the good discriminative value. There were 55 RI exceeding 20% in 102 patients with malignant tumors and 7 exceeding 20% in 29 pa-tients with benign tumors. The tumor focuses were relatively motionless and the physiogenic uptake were disappeared in delayed im-age. Conclusion Dual-phase 18 F-FDG PET/CT improves accuracy in diagnosing malignant tumors and distinguishs between the focus and physiogenic uptake.%目的：探讨18 F-FDG PET/CT双时相显像在肿瘤诊断中的价值。方法102例恶性肿瘤患者及29例良性疾病患者全身PET/CT显像后2h后行局部延迟显像,得到病灶早期最大标准摄取值(SUVmax)和延迟SUVmax,计算滞留指数( RI)。结果恶性肿瘤中,55例RI≥20%,30例5%≤RI<20%,17例RI<5%。良性疾病有7例RI≥20%,7例5%≤RI<20%,15例RI<5%,两者差异有统计学意义( P<0.05)。延迟显像肿瘤病灶相对固定,生理性摄取灶消失；发现部分SUVmax <2的隐匿性病灶。结论双时相显像可以提高PET/CT对良恶性疾病鉴别的准确性,鉴别病灶与生理性摄取。
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