Feasibility assessment of Halcyon 3.0 dual-isocenter IMRT plan in postoperative radiotherapy of radical mastectomy for left side of breast cancer / 中国医学装备

ABSTRACT

Objective:To assess the feasibility of the designed dual-isocenter IMRT plans based on Halcyon 3.0 linear accelerator in postoperative radiotherapy of radical mastectomy for left side of breast cancer.Methods:A total of sixteen patients received the postoperative radiotherapy of radical mastectomy for left side of breast cancer at Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine from December 2022 to June 2023 were retrospectively selected.The dual-isocenter plans based respectively on Halcyon 3.0 linear accelerator and Truebeam linear accelerator were designed,and the dosimetric parameters included conformity index(CI)values of target region,homogeneity index(HI)values and doses to organs at risk(OAR)of the two plans were calculated as statistic method.And then,the dosimetric performance of Halcyon 3.0 dual-isocenter plan was compared and analyzed.Utilizing two dose verification tools,ArcCHECK and Portal Dosimetry,to assess the precision of beam delivery of Halcyon 3.0 dual-isocenter plan.Results:The Halcyon dual-isocenter plan and the Truebeam single-isocenter plan had similar plan quality.There were not statistically significant differences(P>0.05)in dosimetric parameters such as CI,HI,exposure dose to 2%of the target volume(D2%)and exposure dose to 98%of the target volume(D98%).Compared to the average monitor unit(MU)of Truebeam single-isocenter plan,the MU values of Halcyon 3.0 dual-isocenter plan increased by 366 MU,while the difference was not statistically significant(P>0.05).The Halcyon 3.0 dual-isocenter plan provided comprehensive protection for OAR,which was better than that of the Truebeam single-isocenter plan.The values of the left side of lung volume(V20)that were covered by 20 Gy dose of the Halcyon 3.0 dual-isocenter plan and the Truebeam single-isocenter plan were respectively 20.41%±1.56%and 24.88%±2.95%,and the difference was statistically significant(t=6.413,P<0.05).There were not significant differences in other OAR dosimetric parameters between the two kinds of plans(P>0.05).The verification pass rates of the Halcyon 3.0 dual-isocenter plans on the ArcCHECK and Portal Dosimetry platforms were respectively 97.6%-98.9%and 98.1%-100%when the ratio of dose tolerance(DT)to distance to agreement(DTA)was set at 2%/2 mm.The verification pass rates of the Halcyon 3.0 dual-isocenter plans on the ArcCHECK and Portal Dosimetry platforms were respectively 99.1%-100%and 99.7%-100%when DT/DTA was set at 3%/3 mm.The beam delivery precision of the Halcyon 3.0 dual-isocenter plan could meet verification standards of clinical treatments.Conclusion:The Halcyon 3.0 dual-isocenter IMRT plan demonstrates a higher feasibility in the postoperative radiotherapy of radical mastectomy for left side of breast cancer.The precision of dose delivery of plan is high,and the dose of target area is sufficient,uniform and favorable conformability.It can effectively limit the OAR exposure dose at the same time.