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Objective To compare the positioning accuracy between personalized polyurethane foam with wing boards and negative pressure vacuum bag in radiotherapy for lung cancer using kilovoltage cone beam computed tomography(CBCT). Methods Thirty-nine patients with lung cancer who received chest radiotherapy in our hospital from 2015 to 2016 were enrolled as subjects. In those patients, 20 were immobilized by negative pressure vacuum bags(VB group)and the others by personalized polyurethane foam with wing boards(PF group).CBCT images were acquired weekly and registered with planning CT images. Setup errors in the left-right, superior-inferior, and anterior-posterior directions, three-dimensional(3D) displacement vector,and setup time were recorded. The margin of the planning target volume(PTV)was calculated using the Van Herk formula(2.5∑+0.7σ). Between-group comparison was made by paired t test. Results The PF group had a significant smaller setup error in the y-direction than the VB group (2.54±1.79 vs.3.19±2.14 mm,P=0.03),while there were no significant differences in setup errors in the x-or z-direction between the two groups(1.80± 1.48 vs. 1.90± 1.41 mm, P=0.46;2.14± 1.75 vs. 2.25± 1.75 mm,P=0.35). There were no significant differences in rotational setup errors in the Rx-,Ry-,or Rz-direction between the two groups(1.15°±0.76°vs. 1.15°±0.85°, P=0.50;0.71°±0.60°vs. 0.72°±0.43°, P=0.45;0.62°±0.54° vs. 0.46°±0.30°,P=0.06). The PTV margins in the x?,y?,and z?directions were expanded by 5.56, 8.57, and 7.02 mm, respectively, in the PF group, and by 5.62, 9.27, and 7.23 mm,respectively,in the VB group. The proportion of patients with 3D displacement vectors larger than 5 mm was 40% in the PF group and 45% in the VB group.Conclusions For patients undergoing radiotherapy for lung cancer,personalized polyurethane foam with wing boards can,to a certain extent,reduce the setup error in the superior-inferior direction and PTV margin expansion.[Key words] Lung neoplasms/radiotherapy; Polyurethane foam; Vacuum bag; Setup errors;Margin
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Objective To study the set-up errors by CBCT in IMRT with two different immobilization techniques for thoracic and abdominal tumors.Methods Sixty patients with thoracic and abdominal tumor were included in this study and separated into study group and the control group.The study group were immobilized with carbon fiber holder,vacuum bag and thermoplastic mask.The control group were immobilized with carbon fiber holder and thermoplastic mask.CBCT scan and auto-match online 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 was calculated,meanwhile.The grouped t-test of was carried out between these two methods.Results The shift errors in x-,y-,z-dimension of the study group were (0.32 ± 2.58) mm,(-0.40 ± 3.89) mm,(-0.75 ± 2.43) mm.The Mrrv were 5.60 mm,6.08 mm,6.32 mm.The translation set-up errors in x-,y-,z-dimension of the control group were(0.62 ±3.60),(2.44 ± 4.93),(0.66 ±2.85) mm,respectively.The MPrv were 8.07,10.63,6.90 mm,respectively.The t-test value were t =-0.78,-5.11,-4.22,P =0.440,0.000,0.000,respectively.Conclusions The immobilization techniques with carbon fiber holder,vacuum bag and thermoplastic mask would be better than the techniques without the vacuum bag in reducing the setup errors.
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Objective To discuss the clinical value and existing problems of the fixation technology of negative pressure vacuum bag in tumor precise radiotherapy.Methods The fixation technology of vacuum bag was utilized.The relations between the vacuum-bag and the body were marked by laser beam.The corresponding parts in the patient were linked with vacuum-bag by marks for the repetition of patient's body posture.The confirmation method was used to compare the target areas measured by radiation field scale before and after the body position projection.Results The repeatability errors of patient's body posture was not more than 2 mm.The position error at 0? was not more than 2 mm.The average error between the light depth of the suitable shape under the simulator to the treatment plan was 2-3mm.Conclusion It is indicated that in the development of tumor precise radiotherapy process,errors are obviously reduced by using the vacuum air cushion to fix body posture.This method should be applied widely for its high clinical value.