[近距离放射治疗计划计算（125）I粒子食管支架剂量学研究]

Sun H T, Wang J J, Lin L

Department of Radiation Oncology, Peking University Third Hospital, Beijing 100191, China.

Zhonghua Yi Xue Za Zhi. 2018 Nov 6;98(41):3350-3353. doi: 10.3760/cma.j.issn.0376-2491.2018.41.012.

To investigate the dosimetric distribution characteristics of (125)I seed stents with different seed spacing, diameter and length, as well as different (125)I seed activity. The dosimetry table of (125)I seed esophageal stent was derived to provide dosimetry for its clinical application. The self-expanding coated esophagus stent was designed to carry radioactive (125)I seeds with different length, diameter and seed spacing. A cylindrical organic glass model (Thickness 0.8 cm, diameter 20 cm, height 20 cm) was fixed vertically to a cylindrical organic glass containing a solid paraffin (analytical pure) solution. After paraffin cooling and solidification, CT scan was used to transmit image information to TPS. With the center of the bracket as a dot, the cumulative dose at a distance of 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 5.0, 6.0 and 8.0 cm away from the dot was simulated respectively in 0° and 9° direction. The radial cumulative dose with the seed spacing which was 1.0 and 1.5 cm were different by 4.8%, 5.8%, 7.2%, 8.0%, 8.6% and 13.3% respectively under the exposure of 18.5, 22.2, 25.9, 29.6, 33.3 and 37.0 MBq. When the seed spacing was the same as the length of the stent, the radial cumulative dose with the stent which diameter was 1.3, 2.0, 2.4 cm were different by 4.9% vs 3.4%, 4.7% vs 3.8%, 5.4% vs 6.6%, 4.5% vs 5.3%, 4.7% vs 4.8%, 4.8% vs 5.4% respectively under the exposure of 18.5, 22.2, 25.9, 29.6, 33.3 and 37.0 MBq. When the seed spacing was the same as the diameter of the stent, the radial cumulative dose with the stent which length was 8, 12, 16 cm were different by 1.9% vs 1.2%, 1.7% vs 0.8%, 1.6% vs 1.3%, 1.9% vs 1.5%, 1.7% vs 1.8%, 1.6% vs 1.3% respectively under the exposure of 18.5, 22.2, 25.9, 29.6, 33.3 and 37.0 MBq. The radial cumulative dose of the (125)I seed stent is positively correlated with the activity of the radioactive seeds, Which means the dose rate of a certain point of the (125)I seed stent increase with the increase of the activity of the radioactive seeds. The stent of the (125)I radioactive seeds is negatively correlated with the distance, the dose rate of the (125)I seed stents decrease rapidly with the increase of distance.

为研究不同籽源间距、直径、长度以及不同¹²⁵I籽源活度的¹²⁵I籽源支架的剂量分布特征。推导¹²⁵I籽源食管支架的剂量学表格，为其临床应用提供剂量学依据。自行设计可携带不同长度、直径及籽源间距的放射性¹²⁵I籽源的自膨式覆膜食管支架。将一个圆柱形有机玻璃模型（厚度0.8 cm，直径20 cm，高20 cm）垂直固定于盛有固体石蜡（分析纯）溶液的圆柱形有机玻璃容器中。待石蜡冷却凝固后，采用CT扫描将图像信息传输至TPS。以支架中心为点，分别在0°和9°方向模拟距该点1.5、2.0、2.5、3.0、3.5、4.0、5.0、6.0及8.0 cm处的累积剂量。在18.5、22.2、25.9、29.6、33.3及37.0 MBq照射下，籽源间距为1.0和1.5 cm时，径向累积剂量分别相差4.8%、5.8%、7.2%、8.0%、8.6%及13.3%。当籽源间距与支架长度相同时，在18.5、22.2、25.9、29.6、33.3及37.0 MBq照射下，直径为1.3、2.0、2.4 cm的支架的径向累积剂量分别相差4.9%对3.4%、4.7%对3.8%、5.4%对6.6%、4.5%对5.3%、4.7%对4.8%、4.8%对5.4%。当籽源间距与支架直径相同时，在18.5、22.2、25.9、29.6、33.3及37.0 MBq照射下，长度为8、12、16 cm的支架的径向累积剂量分别相差1.9%对1.2%、1.7%对0.8%、1.6%对1.3%、1.9%对1.5%、1.7%对1.8%、1.6%对1.3%。¹²⁵I籽源支架的径向累积剂量与放射性籽源活度呈正相关，即¹²⁵I籽源支架某点的剂量率随放射性籽源活度的增加而增大。¹²⁵I放射性籽源支架与距离呈负相关，¹²⁵I籽源支架的剂量率随距离增加而迅速降低。