Influence of changing the parameters on energy and profiles of helical tomotherapy
10.3760/cma.j.issn.1004-4221.2017.09.018
- VernacularTitle:HT加速器参数调整对射线质及横截面剂量分布影响
- Author:
Bin XIAO
;
Qi YUE
;
Li ZHANG
;
Zhiwei WANG
;
Xiumei YANG
;
Dan GU
;
Jimei DUAN
;
Yong ZHANG
- Keywords:
Helical tomotherapy;
Actinogen;
Dose distribution;
Semiconductor detector
- From:
Chinese Journal of Radiation Oncology
2017;26(9):1072-1076
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the impact of injection current (IC), injection voltage (IV), and pulse forming network (PFN) on energy (depth ratio D20/D10) and profiles of helical tomotherapy, and to improve the quality control for the stability of beam characteristics.Methods The energy and profiles were measured by ion chamber and TomoDose at different values of IC, IV, and PFN, the relationship between the energy and various parameters was evaluated by Pearson correlation analysis, and the changes in profiles were evaluated by comparative analysis.Results The energy had no correlation with IV and PFN values (P>0.05), but had a strong correlation with IC value (P=0.007), which showed a downward trend with the increase in IC.For the profiles in the x direction:(1) in the main beam region (-200 to 200 mm), the shoulder area of the profiles increased regularly with the increase in IC.There were no significant changes for the profiles when the IV values ranged from 6.42 V to 6.54 V, and the shoulder area of the profiles reached the highest point with IV=6.60 V, then decreased with further increase in IV.The shoulder area of the profiles decreased regularly with the increase in PFN.(2) In the penumbral region (±200 mm outside), all the three parameters had no effect on the profiles.For the profiles in the y direction:(1) in the main beam region (-20 to 20 mm), the profiles showed an upward trend in the area with an off-axis distance less than 16 mm when IC values were 5.40 V and 5.46 V, and showed an upward trend in the area with an off-axis distance less than 16 mm.But on the whole, the shoulder area of the profiles increased with the increase in IC, and was not affected by IV and PFN.(2) In the penumbral region (±20 mm outside), the profiles decreased regularly with the increase in IV, and was not affected by IC and PFN.IC had the highest influence on the profiles in the main beam region, followed by PFN and IV.Only IV had impact on the profiles in the penumbral region.Conclusions When the energy needs to be adjusted, the IC value should be given a priority, and PFN should be taken as a supplementary factor.When the profile needs to be adjusted, the IC value should be given a priority, and IV should be used as an auxiliary factor in the main beam region.But in the penumbral region, adjustment of parameters is only related to the profiles in y direction, so the IV value should be adjusted.This study has a guiding role in the quality control of energy and profiles, which can reduce the blindness of quality control, thus saving the time.
