目的 探讨分化型甲状腺癌（DTC）术后131I 全身扫描（WBS）胸腺显影的影像学特征及发生率。 方法 收集2000年至2004年276例DTC术后547次131I治疗后显像。分析胸腺浓聚131I影像学特征、发生率及原因。结果276例DTC术后患者的三次131I治疗后扫描中,纵隔转移灶的阳性率分别为16.2%、35.5%、20.45% ，胸腺摄取的阳性率分别为0%、4.4%、6.8%。10例病人共11次WBS纵隔胸腺显影，其中8例为第二次131I治疗后WBS显影，3例为第三次治疗后，只有一例患者胸腺在第二次治疗及第三次治疗后均持续显影。所有患者结合血清甲状腺球蛋白（Tg）、其他影像学检查及临床随访结果均提示胸腺显影为生理性摄取，而非转移性病变。结论 甲状腺癌术后131I WBS胸腺显影的发生率较低，为131I WBS假阳性的原因之一。

Objective To analyze the frequency and mechanisms of thymus accumulation of iodine-131 on whole body iodine-131 scan (WBS) in post-operative patients with differentiated thyroid cancer (DTC). Methods The total 547 post-treatment whole body iodine-131 scans in 276 patients with differentiated thyroid cancer were collected. The thymus accumulation of 131I on WBS was analyzed. Results The positive rate of radioiodine accumulation in mediastinum in three 131I therapy scan was 16.2%、35.5% and 20.45%, thymus uptake rate were 0%, 4.4% and 6.8% respectively in post-operative patients with DTC. Radioiodine accumulation in thymus was seen on 11 scans in 10 patients. Eight of these were second follow-up scans, three were third scans. Only one patient had persist thymus uptake on both second follow-up scan and third scan. None of these patients have evidence of metastatic disease by correlation with serum thyroglobulin and other imaging findings and clinical follow-up. Conclusion Uptake of radioiodine in the thymus on whole body iodine-131 scan in post-operative patients with differentiated thyroid cancer might be very rare and that will be the cause of a false-positive interpretation.