The Value Of Different STg Levels And ^99mTcO₄^- - Thyroid Imaging In ¹³¹Ⅰ Ablation Of Low And Intermediate Risk Papillary Thyroid Carcinoma In The Early Postoperative Period

Objective:To evaluate the guiding value of the postoperative stimulated thyroglobulin（sTg）in the treatment of low and intermediate risk papillary thyroid carcinoma（PTC）patients with iodine 131 dose,and to discuss the relationship between technetium uptake and iodine uptake of residual thyroid tissue（RTT）and its predictive value for the efficacy of ablation.Materials and Methods:The clinical data of 93 patients with low to intermediate risk PTC in the nuclear medicine department of our hospital during January 2016 to August 2020 were retrospectively analyzed.According to the sTg level before ¹³¹Ⅰtreatment,patients were divided into three groups:sTg<1ng/ml group（n=38）,1ng/ml≤sTg<10ng/ml group（n=39）,sTg≥10ng/ml group（n=16）.Each group was given basal ¹³¹Ⅰ dose of1.11-1.85GBq（30-50mCi）,2.22GBq（60mCi）,2.96GBq（80mCi）,respectively.When^99mTcO₄^--pertechnetate thyroid scintigraphy and ultrasound showed more renmant thyroid tissue or cervical lymph node metastasis,the dose of ¹³¹Ⅰ was upregulated to 2.22,2.96and 3.70GBq in each group.Observe the therapeutic effects of each group and the success rate of ¹³¹Ⅰ ablation of residual thyroid tissue.Qualitative data were expressed as percentage,and quantitative data as （？）±s.Pair t test was used for comparison between groups,and the difference was statistically significant（P<0.05）.A toral of 48 PTC patients were collected after excluding patients with lymph node metastasis,large RTT and ^99mTcO^-₄-thyroid imaging negative.The ^99mTc uptake and ¹³¹Ⅰ uptake of RTT were evaluated by target-to-nontarget(T_99mTc/NT_99mTc、T_131Ⅰ/NT_131Ⅰ)ratio on ^99mTc-pertechnetate thyroid scintigraphy and post-therapeutic whole body scan（Rx-WBS）.The ablation of RTT was comfirmed by the diagnostic whloe body scan（Dx-WBS）.The relationship between T_99mTc/NT_99mTcand T_131Ⅰ/NT_131Ⅰratio of RTT was analyzed by Spearman correlation analysis and the linear regressionequation was established.Factors which may affect the ablation of RTT were assessed by univariate（Fisher exact test and Mann-Whitney U test）.The differences were statistically significant（P<0.05）.Indicators with statistical significance were obtained to establish receiver operating characteristic（ROC）curve,so as to obtain the optimal diagnostic threshold.Results:1.After adjusting ¹³¹Ⅰdose of PTC patients with different levels of sTg combined with thyroid ultrasound and ^99mTc-pertechnetate thyroid imaging,the proportion of good overall efficacy（ER+IDR）was 71.0%（66/93）,and the success rate of ¹³¹Ⅰ treatment was62.4%.2.The ratio of T_99mTc/NT_99mTcdoes not predict the efficacy of ablation while the T_131Ⅰ/NT_131Ⅰratio has a certain value in pradicting the efficacy.There was a positive correlation between T_99mTc/NT_99mTcand T_131Ⅰ/NT_131Ⅰratio and the linear regression equation was y=28.66x+133.Conclusion:1.sTg is an effective indictor for determing the ¹³¹Ⅰ dose of ablation.The treatment of low and intermediate risk PTC patients by grouping according to the efficacy response of DTC and combining ^99mTcO₄^--thyroid imaging and thyroid ultrasound can obtain satisfactory clinical efficacy,which is conducive to the formulation of personalized plan.2.T_99mTc/NT_99mTcratio can not predict the ablation,but there is a linear regression relationship between it and T_131Ⅰ/NT_131Ⅰ,which has a certain predictive value of ablation.It has the function similar to the measurement of thyroid iodine uptake rate,combining with the sTg level will be beneficial to the prediction of iodine-131 dose.