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Objective To explore optimized method of estimating 131I effective half-life(EHL) in patients with Graves' disease(GD).Methods The EHL was obtained by measuring thyroid radioactive iodine uptake (RAIU) of 126 patients (32 males,94 females,average age (38.47± 11.49) years) with GD at 4,24,48,96,120,144,168,192 and 216 h.Two-sample t test,bivariate correlation analysis and curve estimation were used for statistical analysis.Results The EHL of 126 patients was 0.5-7.5 (4.70±1.46) d.The EHL was 3.0-7.5(5.25±1.01) d and 0.5-6.0(3.24±1.52) d in group A (94 patients,without advanced peak of RAIU) and group B (32 patients,with advanced peak of RAIU),respectively,and the difference between the 2 groups was significant (t =8.499,P＜0.01).The EHL had no significant correlation with RAIU4h/RAIU24h(r=-0.177,P＞0.05) in group A,while it had negative correlation with RAIU4h/RAIU24h in group B (r =-0.724,P＜0.01).In group A,the EHL of patients with RAIU24h/RAIU48h ＞100％ was 3.0-7.5 (5.11 ±0.98) d,the EHL of patients with RAIU24h/RAIU48h ≤ 100％ was 4.0-7.0(5.91±0.94) d (t=3.141,P＜0.01).In group B,when RAIU4h/RAIU24h+RAIU24h/RAIU48h was used as the independent variable in S curve model to estimate the EHL,the result was the best (R2=0.930,F=397.22,both P＜0.01,b0 =-3.038 0,b1 =9.659 4).Conclusions In order to optimally estimate EHL,patients should be grouped according to 131I turnover.In patients with advanced peak of RAIU,the EHL should be calculated by using formula of (RAIU4h/RAIU24h +RAIU24h/RAIU48h).If no advanced peak of RAIU exists,patients should be further divided according to RAIU24h/RAIU48h ＞ 100％ or RAIU24h/RAIU48h ≤100％,and the EHL mean value of each group is taken as the estimated EHL.
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Objective To evaluate the variability of calculating thyroid volume by SPECT imaging at different time postinjection. Methods A total of 40 patients with Graves disease were enrolled in this prospective study using simple random sampling method. After intravenous injection of Na99TcmO4, all patients underwent planar and tomographic scintigraphy at different time points (5, 10, 15, 20, 25, 30, 45 and 60 min), and the planar or tomographic integral method were used to estimate thyroid volume. Data were analyzed by one?way analysis of variance, paired t test or linear correlation analysis. Results For thyroid volume esti?mated by planar imaging, the correlation coefficients between the different time points and 20 min were 0?717-0?819 (all P<0.05), and the CV was (18.38±5.31)%. For thyroid volume estimated by tomographic integral method, the correlation coefficients were 0.913-0.961 (all P<0.05), and the CV was (8.05± 3?19)%. Both the correlation coefficient and CV were statistically significant between the two methods ( t=-13.59, -11.29, both P<0.05) . Conclusions Tomographic integral method has better correlation and re?producibility in calculating thyroid volume compared with planar method.