title: Volumetric imaging by megavoltage computed tomography for assessment of internal organ motion during radiotherapy for cervical cancer.
abstract: OBJECTIVE
  To assess the internal organ motion of the cervix and uterus by megavoltage computed tomography (MVCT) during intensity-modulated radiotherapy (IMRT).
  
  
  METHODS
  Ten patients with Stage IIB-IVA cervical cancer underwent daily MVCT imaging. Internal organ motion was evaluated on 150 pretreatment MVCT images by measuring shifts in their boundaries between the MVCT and kilovoltage (kV) planning CT scan in the anterior, posterior, left and right lateral, and superior and inferior direction. Additional intrafractional patient movement was evaluated on 50 posttreatment MVCT images.
  
  
  RESULTS
  Measured cervical motion (mean +/- SD) was 0.4 +/- 10.1 mm in the anterior, -3.0 +/- 6.9 mm in the posterior direction, -3.5 +/- 4.9 mm in the left and 0.2 +/- 4.5 mm in the right lateral direction, 2.2 +/- 8.0 mm in the superior and 0.5 +/- 5.0 mm in the inferior direction. Compared to the cervix, larger uterine motion was observed. Patient movement during treatment was limited to 1.1 +/- 1.3 mm, -0.3 +/- 1.6 mm, and 0.2 +/- 2.3 mm in anteroposterior, laterolateral and superoinferior direction respectively.
  
  
  CONCLUSIONS
  MVCT imaging can be used to study patient setup accuracy and cervical and uterine motion during IMRT. This data may be used to refine treatment margins.
authors.affiliation: Department of Radiotherapy, Oncology Centre University Hospital Brussels (UZ Brussel), Brussels, Belgium. ccollen@uzbrussel.be
authors.forename: Christine
authors.initials: C
authors.lastname: Collen
authors.forename: Benedikt
authors.initials: B
authors.lastname: Engels
authors.forename: Michael
authors.initials: M
authors.lastname: Duchateau
authors.forename: Koen
authors.initials: K
authors.lastname: Tournel
authors.forename: Mark
authors.initials: M
authors.lastname: De Ridder
authors.forename: Samuel
authors.initials: S
authors.lastname: Bral
authors.forename: Dirk
authors.initials: D
authors.lastname: Verellen
authors.forename: Guy
authors.initials: G
authors.lastname: Storme
mesh_terms: D002584:Cervix Uteri / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007047:Hysterosalpingography; D009068:Movement; D015588:Observer Variation; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D014599:Uterus