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Objective To study the dosimetry effect of Dw and Dm middle and lower esophageal cancer in Monaco treatment planning system (TPS). Methods 30 patients with T3N0M0StageⅡa middle and lower esophageal cancer were selected for experiment. For each patient, optimize the plan using dose to water (Dw) and dose to medium (Dm) dose calculation mode, then rescale prescription dose to 95% volume of PTV. Compare the difference in the two mode, conformity index (CI), Homogeneity index (HI), Mean dose (Dmean), Minimum dose (Dmin), Maximum dose (D2), Dose to Organ at risk (OAR), MU, Optimization time, photon usage, and QA results of MatriXX and Arc Check. Use SPSS for multivariate analysis. Results In the dose evaluation of the middle and lower esophageal cancer cases under different dose calculation methods, the spinal cord, trachea, V20 of the whole lung, and D2 of the liver have significant dosimetric differences, the dose value, the sequential dose results were compared as (37.92 ± 1.11)/(35.85 ± 1.08), (59.91 ± 1.43)/(60.25 ± 0.98), (22.52 ± 1.75)/(21.38 ± 2.01), (42.89 ± 0.52)/(41.73 ± 0.58). In the comparison of dose cloud distribution, the difference is mainly located in the cavity and the inner wall of the lung in the target area, the dose in the target cavity in the Dw group is higher than that in the Dm group. The dose in the inner and outer walls of the lung cavity in the Dw group are slightly adducted than that in the Dm group, especially in the central area.Dose QA of MartiXX (3%-3 mm) and Arc Check (2%-2 mm) with different dose calculation methods of 60 plans of 30 cases have all passed clinical requirements. Dm Group is better than Dw group. Conclusion It is recommended to use Dm dose calculation method for Monaco 5.11 TPS in the condition of treatment planning for middle and lower esophageal cancer.
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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.