Dosimetric Comparison Between Margin Expansion Technique and Respiratory Gating Technique Based on 4D CT

CHAN Chengchiuyat; YE Hui-ling; XIAO Qing; LEUNG Vincent Wan Shun; ZHANG Xiang-bin; ZHONG Ren-ming

doi:10.13820/j.cnki.gdyx.20250361

Abstract：Objective To quantitatively evaluate the dosimetric differences and dose delivery accuracy between the margin expansion technique and the respiratory gating technique based on 4D CT,aiming to provide reference for clini-cal radiotherapy modality selection.Methods Treatment plans based on 4D CT were analyzed for 20 patients with lung cancer using both techniques.The evaluation included:(1)Measurement of static dose using a motion platform combined with SRS MapCHECK under static conditions;(2)Measurement of dynamic dose driven by patient-specific respiratory waveforms;(3)Gamma(γ)pass rate evaluation comparing both static and dynamic doses with planned doses;(4)Com-parison of planned dose parameters for target volumes and organs at risk(OARs),as well as treatment times.Results Using the 2％/1 mm γ evaluation criterion,the static γ pass rate for the margin expansion technique was(96.7±3.2)％,while the dynamic rate dropped to(59.9±14.4)％.In contrast,the respiratory gating technique achieved a static γ pass rate of(98.5±2.1)％and a dynamic rate of(90.5±7.3)％.The margin expansion technique exhibited a larger decline in dynamic γ pass rate[(37.9±15.7)％]compared to respiratory gating[(8.1±6.8)％].Dosimetric plan analysis showed that the margin expansion technique had a sharper dose falloff(R50％:3.88±0.28 vs.4.08±0.32),while the respiratory gating technique showed lower mean lung dose(Dmean:2.74±1.34 vs.3.30±1.72 Gy),lung V5(10.69±4.51 vs.12.43±5.29％),lung V20(2.84±1.77 vs.3.48±2.26％),and heart Dmean(2.35±1.64 vs.2.88±2.05 Gy).Conclusion Gamma analysis indicates that the respiratory gating technique provides higher dose delivery accuracy than the margin expansion technique.Additionally,it offers better protection for critical organs such as the lungs and heart.