儿童全脑全脊髓螺旋断层放疗中体位固定技术的对比研究OA

Objective:To compare the positioning errors between thermoplastic mask immobilization technique and vacuum-lock bag immobilization technique for posture in craniospinal irradiation(CSI)utilizing helical tomotherapy(HT)for children,so as to provide basis for optimizing immobilization plan of posture of pediatric patients.Methods:A retrospective analysis was conducted on pediatric patients who underwent CSI at Beijing Shijitan Hospital between January and December 2024.Patients were divided into two groups based on the different immobilization device,thermoplastic mask group(n=6)and vacuum-lock bag group(n=6).The positioning errors were quantified using megavoltage CT(MVCT)verification.The positioning error of the thermoplastic mask group was compared to that of the vacuum-lock bag group at left-right(x)direction,head-foot(y)direction,abdomen-back(z)direction and cross-section rotation(Roll)direction.At the same time,the external boundary of planning target volume(PTV)of two groups were respectively calculated.Results:The positioning errors of the thermoplastic mask group and the vacuum-lock bag group on x,y,z and Roll directions were respectively[0.3 mm(-0.40,0.98),-2.85 mm(-3.68,-1.68),(2.69±1.90)mm and 0.1°(0,0.28)]and[(-0.23±2.91)mm,(-2.90±3.36)mm,(-1.12±2.74)mm and 0.1°(0,1.30)].The positioning error of the thermoplastic mask group was significantly smaller than that of the vacuum-lock bag group on x direction(U=251.0,P<0.001).Under the condition without MVCT verification in each day,the PTV external boundary values of the thermoplastic mask group and the vacuum-lock bag group w ere recommended respectively as(3 mm,5 mm and 5 mm)and(7 mm,8 mm and 7 mm)on x,y and z directions.Conclusion:Both the thermoplastic mask technique and the vacuum-lock bag technique can meet the requirements of posture immobilization in CSI utilizing HT for children,and the conditions of children should be comprehensively assessed in clinical application so as to conduct individual selection for children.