Study On Setup Errors Of Radiotherapy With Three Different Immobilization Techniques For Thoracic And Abdominal Cancer Patients By CBCT

Objective：Study the set-up errors by CBCT in IMRT with three differentimmobilization techniques for thoracic and abdominal tumors.Methods：Ninety patients with thoracic and abdominal tumor were included inthis study and separated into group A、group B and group C. Group A wereimmobilized with carbon fiber holder, vacuum bag and thermoplastic mask. Group Bwere immobilized with carbon fiber holder and thermoplastic mask.Group C wereimmobilized with carbon fiber holder and vacuum bag.CBCT scan and auto-matchonline were regularly performed before the treatment. The setup of left-right(x),superior-inferior(y), anterior-posterior(z) were received. The value of the Mptv wascalculated, meanwhile. The grouped t-test of was carried out between these twomethods.Results：The shift errors in x-, y-, z-axis of the group A respectively were（0.32±2.58）mm,(-0.40±3.89)mm,(-0.75±2.43)mm. The MPTVrespectively were5.60mm,6.08mm,6.32mm. The translation set-up errors in x-, y-, z-axis of the group Bwere(0.56±3.45)mm,(1.51±4.93)mm,(1.15±3.27)mm, respectively. The MPTVwere8.07,10.63,6.90mm, respectively. The translation set-up errors in x-, y-, z-axis of thegroup C were（0.42±2.90）,(-0.64±5.05）,(-2.63±3.16)mm, respectively. The MPTVwere6.4,11.00,7.56mmmm, respectively. The F value were F=0.17,4.96,5.20，P=0.85,0.008,0.006respectively. Conclusions：The immobilization techniques with carbon fiber holder, vacuumbag and thermoplastic mask would be the best in the three kinds of the immobilizationtechniques.