摘要目的:根据美国医学物理学家学会（AAPM）2004年提出的TG43号报告［AAPM TG43（2004）］提供的公式，计算放射性碘-125粒子周围剂量分布，验证放射性碘-125粒子治疗计划系统的计算精度。方法:AAPM TG43（2004）报告在计算单颗放射源周围剂量时提供了两种计算方法，不考虑放射源几何结构的计算方法称之为点源计算方法，考虑放射源几何结构的计算方法称之为线源计算方法。假定单颗活度100 U的Amersham 6711型号放射性碘-125粒子，根据AAPM TG43（2004）号报告提供的两种计算方法计算以下各点剂量，在放射性碘-125粒子0°、90°方向，距离0.5、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6 cm处；45°方向，距离0.71、1.41、2.12、2.83、3.54、4.24、4.95、5.66、6.36、7.07、7.78、8.49 cm处；在临床使用的近距离治疗计划系统variseeds 8.0上分别采用上述两种计算方法计算对应活度、对应型号放射性碘-125粒子周围剂量，使用计划系统自带将点捕捉到模板功能，可以精准找到以上相应点的位置，故采用单次测量以上对应点剂量；并对比两者结果是否具有统计学差异。结果:AAPM TG43号报告采用点源计算方法计算单颗活度100 U的Amersham 6711型号放射性碘-125粒子0°、90°方向的剂量，距离相等的点，剂量相同，距其0.5、1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6 cm处分别是8 082.18、1 870.08、756.58、381.47、217.11、131.91、86.55、58.32、39.97、27.42、19.74、14.13 Gy；45°方向，距离0.71、1.41、2.12、2.83、3.54、4.24、4.95、5.66、6.36、7.07、7.78、8.49 cm处的剂量分别是3 957.37、865.83、329.99、155.69、84.10、48.50、28.49、17.80、11.37、7.38、4.98、3.39 Gy。对于线源计算方法，放射性粒子同上相应距离，0°方向各点剂量分别是3 128.71、755.44、330.30、180.53、107.74、68.56、46.40、32.22、22.70、16.00、11.51、8.24 Gy，90°方向各点剂量8 306.46、1 981.01、802.74、405.38、230.60、140.03、91.83、61.84、42.36、29.05、20.91、14.97 Gy；45°方向，同上相应距离处的剂量分别是4 020.78、877.43、333.49、156.93、84.69、48.81、28.65、17.89、11.42、7.41、4.99、3.40 Gy。采用点源计算方法两者剂量差异最大值（0.3%）在45°方向7.78 cm处，线源计算方法差异最大值（-0.3%）在45°方向8.49 cm处，其他采样点数值差异均<0.3%。Amersham 6711型号碘-125粒子0°、45°、90°方向距离源越近，剂量跌落越快，随距离增加逐渐平缓跌落。结论:近距离治疗计划系统variseeds 8.0和AAPM TG43号报告计算剂量最大差异0.3%，可以精确计算放射性碘-125粒子周围剂量分布，为临床开展放射性粒子碘-125粒子植入治疗肿瘤提供了可靠的工具。

abstractsObjective:According to the formula provided by the TG43 report [AAPM TG43 (2004)] proposed by the American Association of Physicists in Medicine (AAPM) in 2004, we calculated the dose distribution around the radioactive iodine-125 particles, and verified the calculation accuracy of the radioactive iodine-125 particles treatment planning system.Methods:AAPM TG43 (2004) report provides two calculation methods when calculating the dose around a single radioactive source. The calculation method that does not consider the geometric structure of the radioactive source is called point source calculation method, and the calculation method that considers the geometric structure of the radioactive source is called line source calculation method. Assuming a single Amersham 6711 radioactive iodine-125 particle with an activity of 100 U, the following point doses were calculated according to the two calculation methods provided by AAPM TG43 (2004) report, at 0°, 90° directions, distances 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 and 6 cm; In the direction of 45°, the doses at 0.71, 1.41, 2.12, 2.83, 3.54, 4.24, 4.95, 5.66, 6.36, 7.07, 7.78 and 8.49 cm. On the clinically used brachytherapy planning system variseeds 8.0, the above two calculation methods are used to calculate the corresponding activity and the dose around the corresponding type of radioactive iodine-125 particles, and the function of capturing points to templates built in the planning system is used to accurately find the above corresponding point position, using a single measurement of the above corresponding point dose; and comparation of the results were performed to see if there is a statistical difference.Results:The AAPM TG43 report uses point source calculation method to calculate the dose of single Amersham 6711 radioactive iodine-125 particles with activity of 100 U at 0° and 90° directions. The points with the same distance and the same dose are 8 082.18, 1 870.08, 756.58, 381.47, 217.11, 131.91, 86.55, 58.32, 39.97, 27.42, 19.74, 14.13 Gy, respectively, at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 and 6 cm away from them. In the 45° direction, the doses at the distances of 0.71, 1.41, 2.12, 2.83, 3.54, 4.24, 4.95, 5.66, 6.36, 7.07, 7.78 and 8.49 cm are 3 957.37, 865.83, 329.99, 155.69, 84.10, 48.50, 28.49, 17.80, 11.37, 7.38, 4.98 and 3.39 Gy, respectively; For line source calculation method, radioactive particles are at the same distance as above. The doses at each point in the direction of 0° are 3 128.71, 755.44, 330.30, 180.53, 107.74, 68.56, 46.40, 32.22, 22.70, 16.00, 11.51, 8.24 Gy, respectively. The doses at each point in the direction of 90° are 8 306.46, 1 981.01, 802.74, 405.38, 230.60, 140.03, 91.83, 61.84, 42.36, 29.05, 20.91, 14.97 Gy; In the 45° direction, the dose at the corresponding distance as above is 4 020.78, 877.43, 333.49, 156.93, 84.69, 48.81, 28.65, 17.89, 11.42, 7.41, 4.99 and 3.40 Gy, respectively. The maximum dose difference (0.3%) between the two methods is 7.78 cm in the 45° direction, the maximum difference (-0.3%) between the two methods is 8.49 cm in the 45° direction, and the value of other sampling points is less than 0.3%. The closer the Amersham 6711 iodine-125 particles are to the source in the directions of 0°, 45°, and 90°, the faster the dose will drop, and the dose will drop gradually as the distance increases.Conclusion:The brachytherapy planning system variseeds 8.0 and the AAPM TG43 report calculate a maximum dose difference of 0.3%, which can accurately calculate the dose distribution around radioactive iodine-125 seeds, and provide a reliable tool for the clinical implementation of radioactive iodine-125 particles implantation for tumor treatment.