Set-up uncertainties with radiation therapy for nasopharyngeal carcinoma
- VernacularTitle:鼻咽癌放射治疗摆位不确定度的研究
- Author:
Cheng-Guang LIN
;
Guo-Wen LI
;
Lui-Wen LIN
;
Wen-Jie LI
;
Jun HUANG
;
Jian-Xin SU
;
Xiao-Wu DEN
;
Nian-Ji CUI
;
- Publication Type:Journal Article
- Keywords:
Immobilization;
Mask system;
Radiotherapy;
Setup uncertainty;
Nasopharyngeal carcinoma;
Sequential CT scans
- From:
Chinese Journal of Radiation Oncology
2005;0(06):-
- CountryChina
- Language:Chinese
-
Abstract:
Objective This study is to investigate the set-up accuracy of thermoplastic mask used for immobilization of nasopharyngeal carcinoma (NPC) patients being treated by Intensity Modulated Radia- tion Therapy (IMRT).Methods Nineteen patients with early stage nasopharyngeal carcinoma (T1- T2N0M0),treated by fractionated intensity-modulated radiation therapy,underwent repeated CTs during their 6-week treatment course.We evaluated their anatomic landmark coordinates in a total of 85 repeated CT data sets and respective x,y and z shifts relative to their position in the 19 treatment-planning reference CTs.Results The translation in x,y,and z-axes with their mean value derived from both positive and negative set-up errors was-0.84 mm(x-axis),+0.65 mm(y-axis) and +0.01 mm(z-axis).Mean target isocenter translation was (0.89?0.69) mm,(0.82?0.79) mm,(0.95?1.24) mm in x,y and z-direc- tions,respectively.The mean total magnitude vector and 95% CI of isocenter motion were 1.87 mm and 4.65 mm.The data measured over the 6-week fractionated course of treatment revealed a slight deterioration of isocenter accuracy.The 95% CI,considered by us to be a valuable parameter for characterizing the sys- tem,of 4.17 mm for measurement within the first 3 weeks increased to 5.12 mm in the last 3 weeks of treat- ment.Conclusions The sequential CT scanning is a pronounced valuable method of evaluating the quality of departmental specific patient positioning procedures.The thermoplastic mask is eyed as well suited tool for immobilization and repositioning of NPC patients receiving intensity-modulated radiation therapy.
