title: Influence of (99m)Tc-pertechnetate thyroid imaging on radioactive iodine uptake.
abstract: OBJECTIVE
  To observe the influence of (99m)Tc-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 (99m)Tc-pertechnetate. The counts of (99m)Tc and (131)I as well as effective half-life of (99m)Tc (Teff (99m)Tc) were calculated respectively according to the half-life formula. The ratio of (99m)Tc to background counts (1200) was calculated as a reference value to evaluate biokinetics of (99m)Tc.The relationship between the effective half-life of (99m)Tc(Teff (99m)Tc) and the level of free triiodothyronine (FT3), free thyroxine (FT4), and effective half-life of (131)I (Teff (131)I)were also evaluated.
  
  
  RESULTS
  After intravenous injection of (99m)Tc-pertechnetate, (99m)Tc counts at 1h, 25h, 49h, 73h and 169h was (440.16±247.35)×10(4), (11.37±10.67)×10(4), (0.13±0.36)×10(4), (-0.1±0.19)×10(4), respectively, and the ratio of (99m)Tc to background at 1h, 25 h, and 49 h was 3668, 94.75, and 1.08, respectively. The Teff (99m)Tc was (4.41±0.49)h. Inverse correlations were noted between the effective half-life of Teff (131)I 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 (99m)Tc and FT3, FT4 as well as the Teff (131)I.
  
  
  CONCLUSIONS
  Teff (99m)Tc is 4.41h, (99m)Tc-pertechnetate thyroid imaging does not influence RAIU three days after injection of (99m)Tc-pertechnetate. Teff (99m)Tc shows no correlation with the thyroid hormone level and RAIU of Graves's hyperthyroidism.
authors.affiliation: Department of Nuclear Medicine,PUMC Hospital,CAMS and PUMC,Beijing 100730,China.
authors.forename: Ning
authors.initials: N
authors.lastname: Guo
authors.affiliation: Department of Nuclear Medicine,PUMC Hospital,CAMS and PUMC,Beijing 100730,China.
authors.forename: Ke
authors.initials: K
authors.lastname: Yang
authors.affiliation: Department of Nuclear Medicine,PUMC Hospital,CAMS and PUMC,Beijing 100730,China.
authors.forename: Yan-song
authors.initials: YS
authors.lastname: Lin
authors.affiliation: Department of Nuclear Medicine,PUMC Hospital,CAMS and PUMC,Beijing 100730,China.
authors.forename: Tong
authors.initials: T
authors.lastname: Wang
mesh_terms: D000328:Adult; D005260:Female; D006111:Graves Disease / Q000000981:diagnostic imaging*; D006801:Humans; D007457:Iodine Radioisotopes / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D013670:Sodium Pertechnetate Tc 99m; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D013974:Thyroxine / Q000032:analysis; D014284:Triiodothyronine / Q000032:analysis
chemical_list: D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D013670:Sodium Pertechnetate Tc 99m; D013974:Thyroxine