| Xu Yuan,Ma Pan,Xu Yingjie,Men Kuo,Dai Jianrong.A method of determining the prescription isodose line for stereotactic radiotherapy VMAT plan[J].Chinese Journal of Radiological Medicine and Protection,2020,40(6):477-480 |
| A method of determining the prescription isodose line for stereotactic radiotherapy VMAT plan |
| Received:September 24, 2019 |
| DOI：10.3760/cma.j.issn.0254-5098.2020.06.011 |
| KeyWords:Stereotactic radiotherapy Prescription isodose line VMAT Brain metastases |
| FundProject:国家自然科学基金（11875320） |
| Author Name | Affiliation | E-mail | | Xu Yuan | Department of Radiation Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Ma Pan | Department of Radiation Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Xu Yingjie | Department of Radiation Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Men Kuo | Department of Radiation Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | | | Dai Jianrong | Department of Radiation Oncology, National Cancer Center, National Clinical Research Center for Cancer, Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China | dai_jianrong@cicams.ac.cn |
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| Abstract:: |
| Objective To establish a method of determining the prescription isodose line for steretactic radiotherapy (SRT) volumetric modulated arc radiotherapy (VMAT) plan. Methods Eight patients with brain metastases treated with SRT were enrolled. The volume of planning target volume (PTV) ranged from 3.5 to 11.7 cm3 (median 6.1 cm3). Reference VMAT plans were designed for each patient with identical prescription dose. Then, the original PTV was contracted by a few millimeters to form a new target for optimization to get plans with different IDLs. The minimum margin which was needed to be contracted to achieve optimal IDL range for each PTV was also studied. Results To achieve the optimal IDL range, 4 or 5 mm PTV contraction was needed for all patients, and the average IDL was (66.05±0.02)%. Compared with reference plans, the average gradient index (GI) of optimal IDL plans decreased by 20% from 4.05±0.39 to 3.37±0.24 (Z=-2.521, P<0.05). The V40, V30, V5 and mean dose in normal brain tissue decreased by 11.5% (Z=-1.973, P<0.05), 7.2% (Z=-2.105, P<0.05), 12.8% (Z=-2.521, P<0.05) and 8.1%, respectively (Z=-2.382, P<0.05), and there was no statistically significant difference with V20, V10 and conformity index (P>0.05). Conclusions The optimization of IDL for SRT-VMAT plan can be achieved with the method of contracting PTV to form new target for planning. 4 or 5 mm is needed to be contracted to achieve the optimal IDL range, and to get lower GI and protect the normal brain tissue. |
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