Abstract：Objective To explore the clinical effect of standardized radiotherapy with Halcyon V2.0 accelerator in patients with
breast cancer after breast conserving surgery. Methods A total of 41 cases of patients with breast cancer after breast conserving were
randomly selected, and CT simulation positioning, target area and organs at risk were mapped successively. According to the actual
situation of patients, the plan design of volumetric intensity modulated arc therapy (VMAT) was carried out for 17 patients. While 24
patients were designed with fix field intensity-modulated radiation therapy (FF-IMRT). The dose distributions of treatment plans, the
plan verifications of 3D γ passing rate, interfractional in vivo transit dose during treatments, and the setup errors were analyzed and
evaluated. Results All 41 plans satisfied the clinical treatment standard. The mean values of homogeneity index, conformity index
and gradient index were 0.07, 0.90, 2.15 for VMAT and 0.08, 0.81, 1.96 for FF-IMRT. The average passing rate of 3D γ at the dose of
2 mm/2% on the Portal Dosimetry plane was 99.9% for VMAT and 99.6% for FF-IMRT. The mean interfractional in vivo transit dose
during treatments was 86.98% for VMAT and 81.31% for FF-IMRT. Conclusion The results show that the new Halcyon V2.0 ring
accelerator has fast execution efficiency, good dose distribution and reliable planning calculation results in postoperative radiotherapy
for breast cancer, demonstrating the advantages of precision radiotherapy.
