^(99m)TcO_4^-甲状腺显像对甲状腺摄碘-131率测定的影响

Influence of ^(99m)Tc-pertechnetate Thyroid Imaging on Radioactive Iodine Uptake

目的观察Na99mTcO-4甲状腺显像对甲状腺131I放射性计数的影响及其随时间变化的规律。方法以2013年3月至5月在北京协和医院核医学科就诊并已行甲状腺摄碘率(RAIU)测定的40例Graves病甲状腺功能亢进患者为研究对象,静脉注射Na99mTcO-4(185MBq)行甲状腺显像以测定甲状腺面积,采用甲状腺功能仪分别测定患者注射Na99mTcO-4后1、25、49、73、169 h甲状腺内放射性计数,并利用半衰期公式推算25、49、73 h时甲状腺内来自于131I及99mTc的放射性计数,以99mTc/室本底计数(1200)相对值为参考,观察99mTc放射性计数随时间的变化规律及其对RAIU的影响,同时计算出99Tcm在甲状腺内的有效半衰期(Teff99mTc),观察其与游离三碘甲状腺原氨酸(FT3)、游离甲状腺素(FT4)、131I有效半衰期(Teff131I)间的相关性。结果静脉注射Na99mTcO-4后第1、25、49、73h,通过甲状腺功能仪测定出来自99mTc的放射性计数分别为(440.16±247.35)×104、(11.37±10.67)×104、(0.13±0.36)×104、(-0.10±0.19)×104,其与室本底比值分别为3668.00、94.75、1.08、NA。Teff99mTc为(4.41±0.49)h,与FT3、FT4和Teff131I均无明显相关;Teff131I与FT3(r=-0.503,P=0.003)、FT4(r=-0.516,P=0.002)则呈负相关。结论甲状腺功能亢进患者甲状腺内Teff99mTc为4.41 h。注射Na99mTcO-43 d后,Na99mTcO-4甲状腺显像对RAIU测定已无影响。99mTc的有效半衰期与患者甲状腺激素水平和摄碘功能无明显相关性。

Objective To observe the influence of 99mTc-pertechnetate on radioactive iodine uptake （RAIU） in patients with Graves＇ disease （GD） hyperthyroidism after thyroid scintigraphy.Methods Totally 40 patients in whom thyrotoxicosis was diagnosed at Peking Union Medical College Hospital from 2013 March to May were recruited,and RAIU were performed in all patients.Gamma-count rates at 1 h,25 h,49 h,73 h and 169 h were examined respectively after intravenous injection of 185 MBq （5mCi） of 99mTc-pertechnetate.The counts of 99mTc and 131I as well as effective half-life of 99mTc （Teff 99mTc） were calculated respectively accoming to the half-life formula.The ratio of 99mTc to background counts （1200） was calculated as a reference value to evaluate biokinetics of 99mTc.The relationship between the effective half-life of 99mTc （Teff 99mTc） and the level of free triiodothyronine （FT3）,free thyroxine （FT4）,and effective half-life of 131I （Teff 131I） were also evaluated.Results After intravenous injection of99mTc-pertechnetate,99mTc counts at 1h,25h,49h,73h and 169hwas （440.16±247.35） ×104,（11.37±10.67） ×104,（0.13±0.36） ×104,（-0.1±0.19） × 104,respectively,and the ratio of 99mTc to background at 1h,25 h,and 49 h was 3668,94.75,and 1.08,respectively.The Teff 99mTc was （4.41 ± 0.49） h.Inverse correlations were noted between the effective half-life of Teff 131I and level of FT3 （r =-0.503,P =0.003） and FT4 （r =-0.516,P =0.002）,while no significant correlation was found between the Teff 99mTc and FT3,FT4 as well as the Teff TM I.Conclusions Teff 99mTc is 4.41h,99mTc-pertechnetate thyroid imaging does not influence RAIU three days after injection of 99mTc-pertechnetate.Teff 99mTc shows no correlation with the thyroid hormone level and RAIU of Graves＇s hyperthyroidism.