RÉSUMÉ
Objective To compare the effects of two arc(TA)and dual arc(DA)techniques on the dose distribution to the planning target volume(PTV)and organs at risk(OAR)in volumetric modulated arc therapy(VMAT)for lower mid-thoracic esophageal cancer.Methods Ten patients with lower mid-thoracic esophageal cancer who received radiation therapy at some hospital from July 2020 to June 2022 were selected retrospectively.A TA radiation therapy plan and a DA radiation therapy plan were developed for each patient using the Ray Arc module of RayStation 4.7.5.4 planning system,and the two kinds of radiation plans were compared in terms of dosimetric parameters including D2,D5,D50,D95,D98,homogeneity index(HI),conformity index(CI),beam-on time and total monitor unit for PTV and lung V5,V10,V20,V30 and Dmean and heartV30,V40 and Dmean and spine cord Dmax for OAR.SPSS 22.0 was used for statistical analysis.Results TA and DA radiation therapy plans had no significant differences in PTV CI,HI,D2,D5,D50,D95 and beam-on time(P＞0.05),and DA plan had D98 and total monitor unit higher obviously than those of TA plan(P＜0.05).In terms of OARs protection,DA plan had heart V30,V40 and Dmean slightly lower than those of TA plan with non-significantly differences(P＞0.05),while lung V5,V30 and Dmean and spine cordDmax significantly lower(P＜0.05).Conclusion DA technique gains advantages over TA technique in PTV dose distribution and dose to OAR,and the involvement of DA technique in preparing the VMAT plan for esophageal cancer contributes to enhancing the treatment efficacy.[Chinese Medical Equipment Journal,2024,45(1):62-66]
RÉSUMÉ
Object To study the effects of the number of arcs in the treatment of cervical cancer with volumetric modulated arc therapy (VMAT) on the treatment plan, and to provide reference for the selection of the number of arcs in the clinical application.Methods CT images of 10 patients with cervical cancer were selected, it's the radiation therapist that delineated the target area and organs, the prescribed dose was 5040 cGy per 28 times to the target area, and single arc (Arc1), double arc (Arc2) and three (Arc3) plan were designed by RayStation planning system to compare the differences with the dosimetry characteristics of target and organs. The time required for planning optimization was recorded, and the difference between the monitor unit and the delivery time in the three plans was analyzed. A dose validation tool for PTW was used to verify the dose to analyze the influence of the number of arc on the passing rate of gamma verification.Results Single arc plan (Arc1), double arc plan (Arc2) and three arc plan (Arc3) for 10 cases of cervical cancer all proved to meet the clinical requirements. With the increase of arc number, the target area distribution got improved, V40, V45 and Dmean in the organs at risk of rectum, bladder, and femoral head gradually decreased in case of doses of 40 and 45 Gy, and V35, V40 and V45 in the normal tissue were lowered in case of the doses of 35, 40 and 45 Gy. With the increase of the arc number, the optimization time and the delivery time of the plan increased, while the difference between the monitor unit of the three plans was smaller. The passing rate of the three plans was more than 99.5％, and the difference was small.Conclusion Cervical cancer VMAT plan has the target dose distribution and the protection of organs at risk enhanced with the increase of the number of arcs, while the treatment time and cost increased. Therefore, it is necessary to take comprehensive considerations on the number of VMAT plan arcs.