Influence of (99m)Tc-pertechnetate thyroid imaging on radioactive iodine uptake / 中国医学科学院学报

ABSTRACT

<p><b>OBJECTIVE</b>To observe the influence of (99m)Tc-pertechnetate on radioactive iodine uptake (RAIU) in patients with Graves' disease (GD) hyperthyroidism after thyroid scintigraphy.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>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.</p>