分化型甲状腺癌患者131I治疗后体内残留放射性活度的评估

Estimation of residual activities in patients with differentiated thyroid cancer after administration of 131I for therapy

    摘要
  • 摘要:
    目的 评估分化型甲状腺癌（DTC）患者131I治疗后体内残留放射性活度。
    方法 本研究共纳入了35例DTC患者，分为“清甲”（20例）与“清灶”（15例）组，分别于服131I后2、6、24、48、72 h进行131I全身显像及1 m处当量剂量率的测定，以2 h时显像计数和活度作为总计数和总活度。根据各时间点显像计数与2 h的显像计数比值间接估算体内残留放射性活度，并估算患者体内残留放射性活度达到400 MBq时的1 m处当量剂量率。统计学分析采用直线相关与回归分析。
    结果 “清甲”组服131I后2、6、24、48、72 h体内残留131I活度占服131I总活度的百分比分别为99%±4%、86%±6%、35%±10%、12%±8%、7%±8%，“清灶”组分别为99%±1%、91%±7%、47%±17%、11%±9%、4%±6%。“清甲”组服131I后2、6、24、48、72 h的1 m处当量剂量率分别为（157±37）、（120±36）、（35±13）、（11±9）、（9±11）μSv/h，“清灶”组分别为（234±43）、（186±51）、（49±20）、（12±11）、（4±6）μSv/h。体内残留的放射性活度与1 m处当量剂量率呈正相关（r=0.87，P＜0.001）。“清甲”与“清灶”组服131I后48、72 h体内残留放射性活度分别为（432±292）、（265±281）MBq及（731±701）、（277±470）MBq，对应的1 m处当量剂量率为8~11 μSv/h。
    结论 DTC患者服131I后48~72 h体内残留放射性活度达到国家标准规定的400 MBq时，即DTC患者1 m处当量剂量率达到8~11 μSv/h时方可出院。

     

    Abstract:
    Objective To estimate the residual activities of patients with differentiated thyroid cancer(DTC) after administration of 131I for post-operative therapy.
    Methods Thirty-five DTC patients were divided into thyroid remnant 131I ablation therapy group(20 cases)and 131I treatment for metastatic lesions group(15 cases). 131I whole body scan and the determination of equivalent dose rate at 1 meter point were performed to estimate multi-temporal residual activities in each patient 2, 6, 24, 48, and 72 h after administration of therapeutic doses of 131I, respectively. The percentage of residual activities was indirectly estimated in vivo through ratio of multi-temporal calculation of radioactive counts on 131I whole body imaging versus that at 2 h(radioactive counts on 131I whole body imaging and 131I activity at 2 h were regarded as total counts and activities), and furthermore the equivalent dose rate at 1 meter point was indirectly estimated when the residual activities reach to 400 MBq. Correlation and regression analysis were used to evaluate the relationship between residual activities and the equivalent dose rate at 1 m. Statistical significance was accepted at P < 0.05.
    Results The percentage of residual activities were 99%±4%, 86%±6%, 35%±10%, 12%±8%, 7%±8% in thyroid remnant 131I ablation therapy group, and 99%±1%, 91%±7%, 47%±17%, 11%±9% and 4%±6% in 131I treatment for metastatic lesions group at 2, 6, 24, 48 and 72 h after administration of 131I, respectively. The equivalent dose rates at 1 m point were(157±37), (120±36), (35±13), (11±9) and (9±11) μSv/h in thyroid remnant 131I ablation therapy group and (234±43), (186±51), (49±20), (12±11) and (4±6) μSv/h in 131I treatment for metastatic lesions group at 2, 6, 24, 48 and 72 h after administration of 131I, respectively. There is a positive correlation between residual activities and equivalent dose rate at 1 m(r=0.87, P < 0.001). The residual activities were(432±292), (265±281) MBq 48 and 72 h after administration of 131I in thyroid remnant 131I ablation therapy group and (731±701), (277±470) MBq in 131I treatment for metastatic lesions group. At the same point of time, the corresponding range of equivalent dose rate at 1 m was from 8 to 11 μSv/h.
    Conclusion The in vivo residual activity reaches the national standard of 400 MBq in patients with differentiated thyroid cancer 48~72 h after serving 131I and the range of equivalent dose rate at 1 m was from 8 to 11 μSv/h. At this time, radiation isolation could be discharged.

     

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