title: Accuracy and precision of cone-beam computed tomography guided intensity modulated radiation therapy.
abstract: OBJECTIVE
  To assess the accuracy and precision of cone-beam computed tomography (CBCT)-guided intensity modulated radiation therapy (IMRT).
  
  
  METHODS
  A 7-field intensity modulated radiation therapy plan was constructed for an anthropomorphic head phantom loaded with a custom cassette containing radiochromic film. The phantom was positioned on the treatment table at 9 locations: 1 "correct" position and 8 "misaligned" positions along 3 orthogonal axes. A commercial kilovoltage cone-beam computed tomography (kV-CBCT) system (VolumeView, Elekta AB, Stockholm, Sweden) was then used to align the phantom prior to plan delivery. The treatment plan was delivered using the radiation therapy delivery system (Infinity; Elekta AB) 3 times for each of the 9 positions, allowing film measurement of the delivered dose distribution in 3 orthogonal planes. Comparison of the planned and delivered dose profiles along the major axes provided an estimate of the accuracy and precision of CBCT-guided IMRT.
  
  
  RESULTS
  On average, targeting accuracy was found to be within 1 mm in all 3 major anatomic planes. Over all 54 measured dose profiles, the means and standard errors of the displacement of the center of the field between the measured and calculated profiles for each of the right-left, anterior-posterior, and superior-inferior axes were +0.08 ± 0.07 mm, +0.60 ± 0.08 mm, and +0.78 ± 0.16 mm, respectively. Agreement between planned and measured 80% profiles was less than 0.4 mm on either side along the right-left axis. A systematic shift of the measured profile of slightly less than 1 mm in anterior and superior directions was noted along the anterior-posterior and superior-inferior axes, respectively.
  
  
  CONCLUSIONS
  Submillimeter targeting accuracy can be achieved using a commercial kV-CBCT IGRT system.
authors.affiliation: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, Louisiana.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Sutton
authors.affiliation: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, Louisiana; Mary Bird Perkins Cancer Center, Baton Rouge, Louisiana. Electronic address: jfontenot@marybird.com.
authors.forename: Jonas D
authors.initials: JD
authors.lastname: Fontenot
authors.affiliation: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, Louisiana.
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Matthews
authors.affiliation: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, Louisiana; Mary Bird Perkins Cancer Center, Baton Rouge, Louisiana.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Parker
authors.affiliation: Mary Bird Perkins Cancer Center, Baton Rouge, Louisiana.
authors.forename: Maurice L
authors.initials: ML
authors.lastname: King
authors.affiliation: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, Louisiana; Mary Bird Perkins Cancer Center, Baton Rouge, Louisiana.
authors.forename: John P
authors.initials: JP
authors.lastname: Gibbons
authors.affiliation: Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, Louisiana; Mary Bird Perkins Cancer Center, Baton Rouge, Louisiana.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Hogstrom
mesh_terms: D001921:Brain / Q000033:anatomy & histology; D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000592:standards; D061827:Dimensional Measurement Accuracy; D006257:Head / Q000033:anatomy & histology; D006801:Humans; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000592:standards