The differences between Monte Carlo calculated dose-to-medium and dose-to-water for lung cancer IMRT
10.3760/cma.j.issn.0254-5098.2015.09.007
- VernacularTitle:肺癌调强计划在水与介质中蒙特卡罗计算的剂量差异
- Author:
Li CHEN
;
Xiaoyan HUANG
;
Wufei CAO
;
Xinghong YAO
;
Along CHEN
- Publication Type:Journal Article
- Keywords:
Lung cancer;
Intensity-modulated radiotherapy;
Monte Carlo algorithm;
Dose-to-medium;
Dose-to-water
- From:
Chinese Journal of Radiological Medicine and Protection
2015;35(9):670-673
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the differences between Monte Carlo (MC) calculated doseto-water (Dw) and dose-to-medium (Dm) for lung cancers treated with intensity-modulated radiotherapy (IMRT).Methods A total of 10 lung carcinoma patients with 5-field IMRT treatment plans were stratified sampling randomly selected for this study,which were performed on Monaco treatment planning system (TPS) with MC algorithm.Using the patients' own CT images as quality assurance (QA) phantoms,two kinds of QA plan were calculated,one was the Dm,and another was the Dw plan.Dose volume histogram (DVH) parameters and the subtraction of two plans were used to evaluate the spatial distribution of the difference between the Dm and Dw.Results Differences between dose-volume indices computed with Dm and Dw for the PTV65 and PTV50 doses (D50％,D98％ and D2％) were-0.3％,-0.2％,0.3％ and 0.1％,-0.6％,0.4％,respectively,of which the D50％ of PTV65 and D98％ of PTV50 had statistical difference (t =-2.536,-3.776,P ＜ 0.05).For normal tissues,spinal cord,heart,lung and esophagus,the D50％ differences between Dm and Dw were 0.3％,1.1％,-0.2％ and -0.1％,of which the Dm of spinal cord and heart were slightly lower than the Dw (t =2.535,3.254,P ＜ 0.05).For the D2％ of the normal tissues,the differences were 0.3％,-0.6％,-0.7％ and 0.6％,the differences were statistically significant (t =2.311,-4.105,-3.878,6.214,P＜0.05).All the differences were within 2％.Meanwhile planned subtraction analysis showed the differences between the Dm and Dw varied very much with the other body parts of the patient,especially for bone tissues,and the two doses were significant difference (＞ 5％).Conclusion In the course of clinical application,the relative differences between Dm and Dw for lung cancers MC calculations should be noted when considering the dose limitations of bone tissue.
