title: Evaluation of positioning accuracy of four different immobilizations using cone-beam CT in radiotherapy of non-small-cell lung cancer.
abstract: OBJECTIVE
  To evaluate the positioning accuracy of four different immobilizations by use of cone-beam computed tomography guidance for radiotherapy of non-small-cell lung cancer (NSCLC).
  
  
  METHODS
  Sixty-seven patients with NSCLC received conventional or stereotactic body radiotherapy. Of these, 30 were immobilized with a thermoplastic frame (TF), 16 with a thermoplastic frame and active breathing control (TF-ABC), 7 with a stereotactic body frame (SBF), and 14 with a stereotactic body frame and active breathing control (SBF-ABC). Cone-beam computed tomography scans at initial setup and after correction were registered to planning computed tomography. The positional errors in the left-to-right, superior-inferior, and anterior-posterior directions were analyzed. The planning target volume margins were calculated.
  
  
  RESULTS
  The precorrection systematic and random errors ranged from 1.9 to 4.2 mm for TF, 1.9 to 4.3 mm for SBF, 1.2 to 5.8 mm for TF-ABC, and 2.3 to 3.9 mm for SBF-ABC. The postcorrection systematic and random errors ranged from 0.3 to 1.9 mm for the four immobilizations. The planning target volume margins (conventional vs. stereotactic body radiotherapy) were 15.6 vs. 13.9 mm (TF), 14.9 vs. 14.8 mm (TF-ABC), 14.4 vs. 13.4 mm (SBF), and 9.9 vs. 9.4 mm (SBF-ABC) before correction and 7.3 vs. 6.9 mm (TF), 4.0 vs. 3.8 mm (TF-ABC), 7.5 vs. 7.1 mm (SBF), and 4.5 vs. 4.2 mm (SBF-ABC) after correction.
  
  
  CONCLUSIONS
  The positioning accuracies of SBF and TF were similar. Active breathing control increased positioning error but reduced internal margin. Cone-beam computed tomography online correction improved the positioning accuracy of NSCLC patients.
authors.affiliation: Division of Thoracic Tumor, Cancer Center, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Renming
authors.initials: R
authors.lastname: Zhong
authors.forename: Sen
authors.initials: S
authors.lastname: Bai
authors.forename: You
authors.initials: Y
authors.lastname: Lu
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Xu
authors.forename: Xiao-Juan
authors.initials: XJ
authors.lastname: Zhou
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000601:surgery; D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D007103:Immobilization / Q000295:instrumentation / Q000379:methods*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009068:Movement; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D012119:Respiration; D018709:Statistics, Nonparametric; D055815:Young Adult