Clinical Observation Of Radiation Dose Dynamics In Vivo After Postoperative Iodine-131 Treatment In DTC Patients

PART 1 Dynamic Changes of Radioactive Dose in Vivo after¹³¹I Treatment in Differentiated Thyroid CarcinomaObjective:To explore the dynamic changes of radioactive dose in patients with differentiated thyroid cancer（DTC）after ¹³¹I treatment and the related factors affecting patients’discharge.Methods:This is a prospective study.From January 2020 to July 2021,84 patients with moderate and low risk were treated with ¹³¹I for the first time after DTC in our hospital.The dose of ¹³¹I was 3.7-5.5GBq.The whole body dynamic radiation monitoring system was used to measure the residual radioactivity at 0,2,4,6,24,48,72 hours after ¹³¹I treatment after DTC.The relevant clinical data of patients were collected and divided into standard group（n=66）and substandard group（n=18）according to the residual radioactivity in 48 hours,comparing the difference between the different times residual activity in vivo.c²test,two independent samples t test,Mann-Whitney U test and binary Logistic regression analysis were used to analyze the related factors affecting the residual radioactivity in patients 48 hours after ¹³¹I treatment after DTC.Results:Among the 84 patients with DTC after ¹³¹I treatment,the discharge rate was 78%（66/84）at 48h.There was no significant difference in the residual radioactivity between the two groups at 0 and 2 hours（P>0.05）,target group of patients in 4,6,24,48,72h in residual activity was lower than that in group not up to standard（all P<0.05）,all patients had residual radioactivity of less than 400MBq.There were significant differences in the rate of change of residual radioactivity at 4,6,24 and 48h（all P<0.05）.And the change rate of the up-to-standard group was higher than that of the down-to-standard group.The results of statistical analysis showed that blood lipids,24h iodine uptake rate,thyroid dynamic and static imaging,T stage and thyroglobulin（Tg）were the influencing factors of residual radioactivity greater than 400MBq at 48h（all P<0.05）.The above factors were included in the multivariate Logistic regression analysis.The results showed that blood lipids（OR value:7.705,95%CI:1.338～44.365）,thyroid dynamic and static imaging（OR value:5.367,95%CI:1.246～23.115）and 24h iodine uptake rate（OR value:1.936,95%CI:1.045～3.586）were independent risk factors for residual radioactivity in 48h patients.Conclusions:The discharge rate of residual radioactivity at 48h after the first ¹³¹I treatment after DTC was 78%,and most patients can be discharged.Before ¹³¹I treatment,blood lipid,iodine uptake rate in 24h,thyroid dynamic and static imaging are independent influencing indexes that affect whether patients can be discharged from hospital in 48h.PART 2 The Relationship between Residual Radioactivity in Vivo after DTC Surgery and after ¹³¹I Treatment and Success of Clearing Residual Thyroid Tissues after half a yearObjective: To explore The relationship between residual radioactivity in vivo after DTC surgery and after ¹³¹I treatment and success of clearing residual thyroid tissues after half a year.Methods: Ninety-one DTC patients who received ¹³¹I treatment for the first time were selected,relevant clinical data were collected,and the residual radioactivity in vivo at different time points within 72 hours after ¹³¹I treatment was measured for follow-up study.The dose of ¹³¹I for the first time to remove residual thyroid tissue was 3.7±0.185GBq（100±5m Ci）.The residual radioactivity of the patients was measured with a whole-body dynamic radiation monitoring system and the radiation doses of the head and neck were detected.According to the results of follow-up after half a year,the patients were divided into the successful group（successfully clearing residual thyroid tissues）and the failed group（fail in clearing residual thyroid tissues）.c2 test,two independent samples t test and Mann-Whitney U test were adopted to compare the differences between groups,and binary logistic regression analysis was used to analyze the factors that may affect the success of clearing residual thyroid tissues.Results: The success of clearing residual tissues rate of ninety-one DTC patients who received ¹³¹I treatment for the first time was80%（73/91）.There were no significant differences in gender,age and BMI in the successful group and the failed group（all P>0.05）;Ultrasonic imaging and thyroid dynamic and static imaging were significant（all P>0.05）.The residual radioactivity in the whole body and head and neck of the two groups was significantly different at 24h（P < 0.05）,but there was no significant difference at 48 h and 72h（all P>0.05）.Logistic regression analysis revealed various factors including patient the positive rate of ultrasound imaging,the positive rate of thyroid dynamic and static imaging and systemic residual radioactivity at24 h,24h systemic residual radioactivity（OR value:1.071,95%CI:1.019¹.126）and the positive rate of thyroid dynamic and static imaging（OR value :0.680,95%CI:0.042⁰.608）were independent influencing factors for the success of clear a half a year after postoperative ¹³¹I treatment in DTC patients（all P<0.05）.Conclusion: The 24 h systemic residual radioactivity and the positive rate of thyroid dynamic and static imaging in patients after DTC surgery and after ¹³¹I treatment are related to the success of clearing residual tissues after half a year,which can provide a reference for the follow-up individualized treatment of patients.