| 国兵,李建彬,王玮,徐敏,邵倩,卢洁.呼吸运动对部分乳腺外照射靶区剂量学的影响[J].中华放射医学与防护杂志,2016,36(7):496-500 |
| 呼吸运动对部分乳腺外照射靶区剂量学的影响 |
| The impact of respiratory motion for target dose during external-beam partial breast irradiation |
| 投稿时间：2016-01-07 |
| DOI：10.3760/cma.j.issn.0254-5098.2016.07.004 |
| 中文关键词: 部分乳腺外照射 四维CT 靶区位移 剂量体积参数 |
| 英文关键词:External-beam partial breast irradiation Four-dimensional computed tomography Target motion Dosimetrist parameters |
| 基金项目:山东省医药卫生科技发展计划项目（2013WS0346） |
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| 中文摘要: |
| 目的 探讨呼吸运动对部分乳腺外照射（EB-PBI）靶区和危及器官（OAR）剂量学的影响。方法 选取保乳术后符合EB-PBI条件的20例患者，在四维CT（4D-CT）10个时相上，由同一勾画者基于术腔边界金属夹结合术腔血清肿勾画靶区（TB）。以0时相为参考时相，制定三维适形放疗计划（3D-CRT），并将0时相的3D-CRT复制到其余9个时相上。观察呼吸周期中呼吸运动导致的靶区及OAR剂量学变化，其中相关剂量学参数如下：平均剂量（Dmean）、均匀性指数（HI）、适形度指数（CI）以及接受x Gy照射的百分体积（Vx）。结果 自由呼吸状态下TB在左右、前后、头脚方向上的位移中位数分别为0.90、0.75和0.80 mm，三维位移矢量中位数为0.95 mm。在头脚方向上，TB位移与靶区Dmean、HI和CI具有相关性（r=-0.458、-0.451和0.462，P < 0.05），尤其与靶区Dmean呈负相关，并且TB位移在头脚方向上与患侧正常乳腺的Dmean、V20和V30呈正相关（r=0.527、0.488和0.526，P < 0.05）。在三维运动矢量上，TB位移与患侧肺的Dmean、V5、V10和V20呈正相关（r=0.416、0.503、0.522和0.498，P < 0.05）。心脏的Dmean、V5和V10仅与心脏体积变化相关（r=0.727、0.704和0.695，P < 0.05）。 结论 自由呼吸状态下呼吸运动引起EB-PBI靶区小幅度的位移能引起靶区剂量学的变化，从而有可能造成照射过程中靶区剂量脱靶或漏照。肺脏受照剂量体积参数的变化受靶区位移及胸廓扩张的双重影响，但心脏受照剂量受呼吸运动的影响并不显著。 |
| 英文摘要: |
| Objective To evaluate the impact of respiratory motion for dose of target and organ at risk during external-beam partial breast irradiation (EB-PBI). Methods 4D-CT scan sets were acquired for 20 patients who underwent EB-PBI. The volume of the tumour bed (TB) was determined based on seroma or surgical clips on the ten sets of 4D-CT images. For each patient a conventional 3D conformal plan (3D-CRT) was generated based on the 4D-CT end inhalation phase images, then copied and applied to the other phases. The following parameters were calculated to analyse: mean dose (Dmean), homogeneity index (HI), conformal index (CI), and the volumes that received ≥ x Gy (Vx). Results During free breathing, the TB centroid motion was 0.90, 0.75 and 0.80 mm in the lateral, anteroposterior and superior-inferior directions, respectively. The medium spatial motion vector was 0.95 mm. In the superior-inferior direction, TB motion significantly correlated with Dmean, HI, and CI of PTV (r=-0.458, -0.451 and 0.462, P < 0.05), as well as Dmean, V20 and V30 received by the ipsilateral normal breast (r=0.527, 0.488 and 0.526, P < 0.05). And in the motion vector, the Dmean, V5, V10, V20 of the ipsilateral lung all correlated with TB motion (r=0.416, 0.503, 0.522 and 0.498, P < 0.05). A correlation also existed between dose and percent volume of heart and volume variation of heart (Dmean, V5 and V10) (r=0.727, 0.704 and 0.695, P < 0.05). Conclusions Small TB motion caused by respiratory motion during free breathing result in dosimetric variation of the target and potential dosimetric off-target or suboptimal dose coverage for EB-PBI. The doses of lung during free breathing were relatively sensitive to TB motion and thorax expansion, while heart doses were not influenced notably. |
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