Correlation between external dose equivalent rate and residual radioactivity in patients with differentiated thyroid carcinoma after 131I therapy / 中华核医学与分子影像杂志

ABSTRACT

Objective To investigate the correlation between external dose equivalent rate (EDER)and residual radioactivity in DTC patients after 131I therapy.Methods A total of 70 DTC patients (15 males,55 females;average age (45.7±12.8) years) who received 131I therapy from January 2015 to May 2015 were reviewed.Patients were divided into remnant ablation group (Group 1,43 patients) and the group of therapy for persistent disease (Group 2,27 patients).The determination of dose equivalent rate at 1,2 and 3 m from the patients was performed at 1,6,18,24,30,42,48,54,66 and 72 h after the administration of 131 I.Simultaneously,the residual radioactivity was estimated through collecting their urine and monitoring the excretion of radioactivity.The correlation between EDER and residual radioactivity was analyzed.Results The functions of standard EDER (μSv · h-1 · MBq-1) at 1 m from the patients of Group 1 and Group 2 were H=0.044 77e-0.063 8t +0.015 04e-0.396t.and H=0.039 71e-0.0629t +0.014 12e-0.325t,respectively.And the functions of residual radioactivity (MBq) of the two groups were A =A0(0.84e-0.061 7t+ 0.16e-0.158 4t)and A =Ao(0.69e-0.087 7t+ 0.31e-0.047 3t),respectively.There was a positive correlation between EDER and residual radioactivity in DTC patients after the administration of 131I (r=0.95,P＜0.001).The fitting function of the dose equivalent rate at 1 m from the patients was H(μSv/h)=0.048A (MBq).Conclusions The residual radioactivity in DTC patients after 131 I therapy can be estimated by determining the EDER.The dose equivalent rate at 1 m from the patients of lower than 19.2 μSv/h can be used as the limitation of radiation isolation.