ABSTRACT
Background and purpose:Intensity-modulated radiotherapy(IMRT) can significantly improve the dosimetric distribution of both the target and organs at risk compared to tangential irradiation for whole breast. However,its optimized methods remain different and conflicting for many radiotherapy institutions.In order to achieve the optimized planning of IMRT for the irradiation of intact breast,we investigated different optimizing methods in three dimensional radiotherapy planning system.Methods:Ten patients with early-stage breast cancer after breast conserving surgery were eligible for the study.Two kinds of plans were performed on each patient in three-dimensional treatment planning system,inverse planning IMRT and forward planning IMRT which included 3 different optimizing methods as manual optimizing(MO),multiple points optimizing(PO) and automated inverse optimizing(AO).Various parameters were used to evaluate the efficacy of different IMRT plans.All plans were compared using dose volume histograms(DVH) for the planning target volume(PTV) and organs at risk(OARs).Results:For MO,PO,AO forward plans and inverse plans,median number of segments were 5,5.5,5 and 20 respectively,and mean total MU were 225.8, 228.4,226.4 and 345.8 MU,respectively.Comparing the different forward planning optimizations,the best target coverage and dose homogeneity of PTV was observed in AO plans(P(?)0.01),and PO and AO plans showed a better reduction of OARs exposure compared with MO plans(P(?)0.05).A further improvement of dose homogeneity in the PTV and better sparing of OARs was achieved using inverse planning(P(?)0.05).Conclusion:Forward planning IMRT with AO optimization for intact breast irradiation could provide both efficacy and dosimetric advantages better than others.The inverse IMRT plan showed more potential in improving the dosimetric outcomes.However,further studies are required for inverse optimizing plans.
ABSTRACT
Background and purpose:Coventional radiation has been used for decades,but the 3D dose distribution has not been studied as yet.In this study,different treatment plans of conventional irradiation technique for esophageal carcinoma have been evaluated by 3-D TPS.Methods:Five patients with esophageal carcinoma at upper-thoracic and five patients at middle-thoracic were enrolled in this study.Three conventional treatment plans were created for each patient,with a prescribed dose of 70 Gy.For tumor at upper-thoracic,plan 1 consisted of one anterior field and bilateral posterior oblique fields with wedges,plan 2 consisted of anterior bilateral oblique fields with wedges ,plan 3 consisted of a pair of AP-PA portals,then followed by right anterior oblique portals and left posterior oblique portals to spare spine cord.For tumor at middle thoracic,plan 1 consisted of one anterior field and bilateral posterior oblique fields.Plan 2 consisted of a pair of AP-PA portals and followed by another pair of parallel-opposed lateral off- cord fields as boost.Plan 3 used the same plan as for the lesion at upper-thoracic.The evaluation of each treatment plan was carried out by dose-volume histogram(DVH).Results:For tumor at upper-thoracic,on average,the maximum dose to spinal-cord in plan 3 was (57.1?4.9)Gy,and was higher than that in plan 1 and plan 2.Plan 1 increased mean lung dose from (12.8?2.1)Gy to (18.2?4.1)Gy(P=0.045)compared with plan 2,but it improved the homogenous dose of PTV2,especially in the patient with long tumor.For tumor at middle-thoracic,on average,plan 2 increased mean lung dose from (11.9?1.1)Gy to (13.0?0.6)Gy(P=0.045) compared with plan 3.Plan 2 increased V_(20) and V_(30) from (23.6?2.3)% to (29.2?1.9)%(P=0.004) and (13.9?2.3)% to (20.9?1.3)%(P=0.006) compared with plan 1.The trachea volume of(?)70 Gy(V_(70))in plan 3 was larger than that in plan 1[(20.3?15.9)% VS (10.5?9.8)%,P=0.058].Conclusion:For tumor at upper-thoracic,plan 1 and 2 were superior to plan 3.Irradiation to lung in plan 2 was lower than that in plan 1,but plan 1 improved the homogenous dose of PTV2 compared with plan 2,especially for patient with longer lesion.For tumor at upper-thoracic,plan 2 increased irradiation dose to lung compared with plan 1 and plan 3.Plan 1 was comparable with plan 3,but the dose of trachea in plan 1 may lower than that in plan 3.