甲状腺癌术后患者纵隔浓聚^131Ⅰ的临床分析

Mediastinai accumulation of ^131I in post-operative patients with thyroid cancer

目的探讨分化型甲状腺癌（DTC）手术及^131Ⅰ治疗后患者全身扫描（RxWBS）示纵隔浓聚^131Ⅰ的影像学特征。方法收集1998-2004年收治的331例DTC术后患者共1183次^131Ⅰ治疗后5-7d的RxWBS图像，所有患者至少接受2次^131Ⅰ治疗，结合甲状腺球蛋白（Tg）测定、其他影像学检查及临床随访结果分析纵隔浓聚^131Ⅰ的影像学特征及原因。结果331例患者中最终诊断为纵隔浓聚^131Ⅰ者共34例，其RxWBS主要表现为纵隔点状、团块状、哑铃状或弥漫性放射性浓聚灶。其中甲状腺癌转移者21例，残留甲状腺组织8例，其余5例胸腺摄取^131Ⅰ患者年龄均〈45岁。结论DTC术后患者纵隔浓聚^131Ⅰ可归因于甲状腺癌转移灶、甲状腺组织及胸腺摄取等。胸腺摄取^131Ⅰ是45岁以下甲状腺癌术后患者RxWBS假阳性的重要原因之一，血清风测定及^131ⅠSPECT／CT、CT增强扫描、MRI等有助于明确诊断。

Objective To analyze the mechanisms of mediastinal accumulation of ^131I in post-operative patients with thyroid cancer, a retrospective study of patients with differentiated thyroid cancer （DTC） was performed. Methods Three hundred and thirty-one consecutive patients with DTC during the period of 1998-2004 were reviewed. Each patient received at least two therapeutic doses of ^131I. Mediastinal accumulation of ^131I on post treatment whole body scans （RxWBS） taken 5 -7 d post therapy was analysed and correlated with serum thyroglobulin, other imaging findings and clinical follow-up. Results Radioiodine accumulation in mediastinum was noted in 34 patients. The pattern of mediastinal activity was classified as ＂focol＂ , ＂ mass-like＂ , ＂diffuse＂ or ＂ dumbbell＂ configuration. The mediastinal ^131I activity was attributed to metastasis in 21 patients, functioning thyroid tissue in 8 patients, and thymus in 5 patients. All 5 patients with thvmus uptake were under 45 years of age. Conclusions Differential possibilities of mediastinal accumulation of ^131I include metastasis, ectnpie thyroid tissue, and thymus uptake. It is important to recognize that uptake of ^131I by the thymus in patients under 45 years of age can be a potential cause of false-positive therapy scans. Serum thyroglobulin measurement and other imaging mndalities, including ^131I SPECT/CT, contrasted CT anti MRI, are helptul ancillary findings for further differentiation.