Influence of helical tomography radiotherapy planning parameters on threading effect
10.19745/j.1003-8868.2025144
- VernacularTitle:螺旋断层放疗计划参数对螺纹效应的影响研究
- Author:
Ruo-qi CAO
1
;
Xia-yu HANG
1
;
Hua HUANG
1
;
Xian-qiang SONG
1
;
Jin-da ZHOU
1
;
Yun-jie BAI
1
;
Xiang-dong SUN
1
;
Yi-kun LI
1
Author Information
1. 东部战区总医院放射治疗科,南京 210002
- Publication Type:Journal Article
- Keywords:
helical tomotherapy;
threading effect;
screw pitch;
lead gate width;
computational grid
- From:
Chinese Medical Equipment Journal
2025;46(8):58-66
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the influence of helical tomographic radiotherapy plans with different combinations of lead gate width,pitch and algorithms on threading effects.Methods A target model was established with a Cheese Phantom used as the simulated human body,then three lead gate widths(1.0,2.5,and 5.0 cm),six screw pitches(0.143,0.172,0.215,0.287,0.430,and 0.500)and two computational grids(Fine algorithm and Normal algorithm)were respectively combined for designing the helical tomography radiotherapy plans.The radiotherapy plans with a pitch of 0.143,0.172,0.215,0.287 or 0.430 were enrolled into an experimental group,and the plans with a pitch of 0.500 were divided into a control group.The dosimetric parameters including maximum dose(Dmax),minimum dose(Dmin)and mean dose(Dmean)of the target area PTV1 and PTV2 were evaluated by the dose volume histogram(DVH).The dose homogeneity index(HI)of the target area was calculated,and the single rotation time and total treatment time of each plan were recorded and counted.SPSS 27.0 software was used for statistical analysis.Results No significant threading effect appeared regardless of the pitch value when the lead gate width was 1.0 cm.The threading effects in the experimental group were weaker than those in the control group when the lead gate width was 2.5 or 5.0 cm.The threading effect gradually rose with the pitch increased when the lead gate width was 5.0 cm.The most significant difference was found between the threading effect in case of the screw pitch being 0.500 and that with the screw pitch being 0.143,with the differenes being statistically obvious(P<0.05).The lead gate width had significant effects on the Dmax,Dmin,Dmean and HI of PTV1 and PTV2.When the lead gate width was 5.0 cm,high HI value and uneven dose distribution were detected and lowered screw pitch weakened the threading effect.The single rotation time first remained constant and then increased with the screw pitch was enlarged,with the changing points occurring in case of the screw pitches of 0.287 and 0.430.With a certain lead gate width,the treatment time for plans was shortened with the decrease of the pitches in case of the pritches lower than 0.287,and tended to be constant after the screw pitches reached 0.287.The changes of the computational grid had no significant effects on the results of radiotherapy plans when the lead gate width and screw pitch were kept constant.Conclusion When designing a spiral tomotherapy plan with conventional doses,a lead gate width of 1.0 or 2.5 cm and a screw pitch of 0.287 or 0.430 should be selected in order to minimize the threading effect while ensuring the efficiency of plan implementation.[Chinese Medical Equipment Journal,2025,46(8):58-66]
