Dosimetric study of hippocampal protective whole brain radiotherapy based on Varian accelerator / 中国辐射卫生

ABSTRACT

Objective The purpose of this study is to provide a reference for the selection of clinical radiotherapy plan by comparing the difference of dosimetry between coplanar dynamic intensity modulation dIMRT and coplanar VMAT plan in hippocampal protective whole brain radiotherapy (WBRT). Methods 10 patients were selected whose hippocampal were protected by WBRT, dIMRT and VMAT plans were designed for each patient, the differences of target dose, organ-endangering dose and machine hop count were compared between the two groups. Results The two technical plans PTV V30 Gy, D98% and D2% all meet the standard of RTOG 0933, which is better than the dIMRT group for the PTV HI VMAT group (P = 0.004). The hippocampal dose of dIMRT group was better than that of VMAT group, but it did not meet the standard of RGOT 0933. The average Dmax of hippocampus in dIMRT group and VMAT group was 18.44 Gy and 19.30 Gy, respectively (P = 0.004). The average value of hippocampal Dmin was 10.03 Gy and 10.77 Gy, respectively (P = 0.013), and the mean value of hippocampal Dmean was 14.20 Gy and 15.12 Gy, respectively (P = 0.002). The doses of lens, eyeball and optic nerve all met the standard of RTOG0933, and the dose of dIMRT group was significantly better than that of VMAT group (P = 0.000). The treatment time in VMAT group was significantly lower than that in dIMRT group. The treatment time in VMAT group was significantly lower than that in dIMRT group. Conclusion Varian dIMRT has more advantages in controlling hippocampal dose and protecting lens than VMAT, but PTV HI and treatment efficiency are higher in VMAT group.