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分化型甲状腺癌(differentiated thyroid cancer,DTC)占甲状腺癌的90%左右,131I治疗是部分DTC患者术后的重要环节[1-2],但是131I的γ射线能量高,穿透力较强,甲状腺癌治疗剂量大,极易对周围产生外照射,是核医学治疗中辐射防护最受关注的一类核素[3],131I治疗患者体内残留活度已成为很多国家判定患者出院的一个标准。
本研究收集了35例DTC患者,通过对患者服用131I后入院期间的观察,以显像法评估患者131I治疗后体内残留的放射性活度,并且结合1 m处当量剂量率的测定评估不同时间点患者体内残留放射性活度对周围的辐射水平,以体内残留放射性活度400 MBq为节点估算患者住院隔离的时间和出院时对周围的辐射水平,为接受131I治疗的患者出院后体内残留的放射性活度对周围环境的影响提供参考。
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“清甲”和“清灶”治疗患者服131I后2、6、24、48、72 h体内残留131I活度占服131I总活度的百分比见表 1,由表 1可见,患者服131I后随时间变化体内残留放射性活度逐渐减少,6~24 h时下降幅度最大,24 h后体内残留放射性活度较之前明显减少,72 h以后较之前显著减少。其中1例“清甲”与1例“清灶”患者服131I后不同时间的全身显像变化见图 1、图 2。
组别 例数 体内131I放射性活度(MBq) 2 h 6 h 24 h 48 h 72 h 清甲组 20 3667±14
(99%±4%)3171±232
(86%±6%)1289±406
(35%±10%)432±292
(12%±8%)265±281
(7%±8%)清灶组 15 5890±1153
(99%±1%)5439±1284
(91%±7%)2901±1416
(47%±17%)731±701
(11%±9%)277±470
(4%±6%)表 1 显像法估算分化型甲状腺癌患者体内131I放射性活度变化
Table 1. The change of the residual activities of patients with differentiated thyroid cancer through 131I whole body imaging
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35例DTC患者服131I前室内的辐射当量剂量率本底为0.2~0.4 μSv/h,“清甲”和“清灶”治疗患者服131I后2、6、24、48、72 h的1 m处当量剂量率见表 2,由表 2可见,1 m处当量剂量率在2 h时达到高峰,6 h时开始下降,24 h时下降幅度>50%,48 h时较之前明显下降,72 h时较之前显著降低。
组别 例数 1 m处当量剂量率(μSv/h) 2 h 6 h 24 h 48 h 72 h 清甲组 20 157±37 120±36 35±13 11±9 9±11 清灶组 15 234±43 186±51 49±20 12±11 4±6 表 2 分化型甲状腺癌患者服131I后不同时间1 m处当量剂量率变化
Table 2. The change of the equivalent dose rate at 1 meter point of patients with differentiated thyroid cancer at different time
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根据显像法估算得出,患者体内残留的放射性活度与服131I后不同时间的1 m处当量剂量率呈线性相关,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),即随着时间的延长,患者体内残留的放射性活度与1 m处当量剂量率均呈下降趋势。
根据显像法估算不同时间“清甲”与“清灶”患者体内残留放射性活度,显示两组患者服131I后体内残留放射性活度均随时间延长而降低,“清甲”及“清灶”患者服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,可见患者于服131I后48~72 h达到国家标准规定的400 MBq。显像法测定的体内残留放射性活度和1 m处当量剂量率的48 h和72 h回归方程分别为y=1.26x+0.45,y=0.87x+1.54,其中y为体内残留放射性活度,x为1 m处当量剂量率,当体内残留放射性活度达到国家标准规定的400 MBq时,对应的1 m处当量剂量率为8~11 μSv/h。
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
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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。 -
关键词:
- 甲状腺肿瘤 /
- 碘放射性同位素 /
- 体层摄影术,发射型计算机,单光子
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. -
表 1 显像法估算分化型甲状腺癌患者体内131I放射性活度变化
Table 1. The change of the residual activities of patients with differentiated thyroid cancer through 131I whole body imaging
组别 例数 体内131I放射性活度(MBq) 2 h 6 h 24 h 48 h 72 h 清甲组 20 3667±14
(99%±4%)3171±232
(86%±6%)1289±406
(35%±10%)432±292
(12%±8%)265±281
(7%±8%)清灶组 15 5890±1153
(99%±1%)5439±1284
(91%±7%)2901±1416
(47%±17%)731±701
(11%±9%)277±470
(4%±6%)表 2 分化型甲状腺癌患者服131I后不同时间1 m处当量剂量率变化
Table 2. The change of the equivalent dose rate at 1 meter point of patients with differentiated thyroid cancer at different time
组别 例数 1 m处当量剂量率(μSv/h) 2 h 6 h 24 h 48 h 72 h 清甲组 20 157±37 120±36 35±13 11±9 9±11 清灶组 15 234±43 186±51 49±20 12±11 4±6 -
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