| Guo Bing,Li Jianbin,Wang Wei,et al.The impact of respiratory motion for target dose during external-beam partial breast irradiation[J].Chinese Journal of Radiological Medicine and Protection,2016,36(7):496-500 |
| The impact of respiratory motion for target dose during external-beam partial breast irradiation |
| Received:January 07, 2016 |
| DOI：10.3760/cma.j.issn.0254-5098.2016.07.004 |
| KeyWords:External-beam partial breast irradiation Four-dimensional computed tomography Target motion Dosimetrist parameters |
| FundProject:山东省医药卫生科技发展计划项目（2013WS0346） |
| Author Name | Affiliation | E-mail | | Guo Bing | School of Medicine and Life Sciences, University of Jinan-Shandong Academy of Medical Sciences, Jinan 250022, China | | | Li Jianbin | Department of Radiation Oncology, Shandong Cancer Hospital Affiliated to Shandong University, Jinan 250117, China | lijianbin@msn.com | | Wang Wei | Department of Radiation Oncology, Shandong Cancer Hospital Affiliated to Shandong University, Jinan 250117, China | | | Xu Min | Department of Radiation Oncology, Shandong Cancer Hospital Affiliated to Shandong University, Jinan 250117, China | | | Shao Qian | Department of Radiation Oncology, Shandong Cancer Hospital Affiliated to Shandong University, Jinan 250117, China | | | Lu Jie | Department of Radiation Oncology, Shandong Cancer Hospital Affiliated to Shandong University, Jinan 250117, China | |
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| Abstract:: |
| 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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