Comparison Between Dmlc-IMRT And VMAT Plan For The ENI Mode Of Cervical Esophageal Cancer

ObjectiveComparison between dynamic multi-leaf collimator intensity modulated radiotherapy(dmlc-IMRT)and volumetric modulated arc therapy(VMAT)in the treatment of cervical esophageal cancer(CEC).MethodsCT datasets of 9 patients with CEC were collected.Two plans were generated for each patient:dmlc-IMRT with 7 fixed fields(7f-dmlcimrt)and VMAT(a full counter-clockwise arc with a avoidance sectors,from 300°to 210°,or 150°to 60°).The prescription dose of primary tumor was 60Gy/30F,while that of clinical target volume was 54Gy/30F.The dose-volume histogram data,the number of monitoring units(MUs)and the treatment time(TT)for different plans were compared.ResultsThe D2 and V105 for the planning target volume(PTV)in vmat plan were higher than those in 7f-dmlcIMRT plan,while the Dmean and D98 were opposite.In terms of the coverage of target,the V95 and V98 for the PTV in 7th-dmIcIMRT plan were superior to those in the VMAT plan.The VMAT program only performed well on the the conformal index(CI)of planning target volume for the gross tumor volume(PGTV),while the CI of planning target volume for the clinical target volume(PCTV)did not differ from that in the 7f-IMRT program.The homogeneity indexs(HI)of PTV in VMAT plan were weaker than those in the 7f-dmlcIMRT plan.The Dmax of spinal cord were similar in two plans.The Dmean,V20 and V30 for lung in VMAT plan were significantly higher than those in 7f-dmlc IMRT plan(P<0.05),and V5,V10 and V13 were also higher than those in 7f-dmlc IMRT plan(P>0.05).And the dose of thyroid gland in VMAT plan were lower than those in 7f-dmlcIMRT plan,but there were no statistical differences.In the VMAT plan,the V50 and V54 for the brachial plexus were reduced comparing with those in the in7f-dmlc IMRT plan,while the V58 and V60 for the brachial plexus were not significantly different.The delivery efficiency of the VMAT program was higher than that of the 7f-dmlc IMRT.The VMAT program reduced the average MU by 11.1%compared to the 7f-dmlc IMRT program,reducing the treatment time by 50%.ConclusionThe VMAT program was not less than or equal to 7f-dmlc IMRT in target area dose,but significantly reduced the number of required MUs and the TT.