title: Setup margins and geometric uncertainties in intensity-modulated radiation therapy in treating pituitary adenomas: the experience of Lyon Sud Hospital.
abstract: OBJECTIVE
  The authors retrospectively evaluated the setup uncertainties in Intensity-Modulated Radiation Therapy (IMRT) for pituitary adenomas and verified the margins used in daily practice (3 mm).
  
  
  METHODS
  Craniocaudal (CC), anteroposterior (AP) and laterolateral (LL) displacements were measured during the first 3 days of treatment and then weekly by comparing two orthogonal images obtained by an electronic system of portal imaging with Digitally Reconstructed Radiographs (DRRs). Setup Margins (SM) were defined according to the International Commission on Radiation Units (ICRU)-62 formula, the Stroom equation and the van Herk equation. The systematic (Σ) and random (σ) errors of the population were calculated as standard deviation (SD) of the population mean and the mean of SDs for every patient, respectively.
  
  
  RESULTS
  Twenty patients were treated by IMRT for pituitary adenomas, and a total of 231 measurements were obtained. Σ and σ were 0.6 and 1.3 mm, 0.8 and 1 mm, 1.2 and 1.5 mm in the AP, LL and CC direction, respectively. Larger setup margin was 2.4, 2.7 and 4 mm in the AP, LL and CC direction, respectively (van Herk formula).
  
  
  CONCLUSIONS
  IMRT is a highly sophisticated treatment technique that requires precise definition and optimisation of local setup errors and, finally, of the irradiated volumes. The role of image-guided RT in these kinds of treatments should be prospectively evaluated.
authors.affiliation: Service de Radiothérapie Oncologi, Centre Hospitalier Lyon-Sud, Chemin du Grand-Revoye, 69495, Pierre Benite Cedex, France. bdebari@yahoo.it
authors.forename: B
authors.initials: B
authors.lastname: De Bari
authors.forename: I
authors.initials: I
authors.lastname: Shakir Shakir
authors.forename: T
authors.initials: T
authors.lastname: Chekrine
authors.forename: L
authors.initials: L
authors.lastname: Lestrade
authors.forename: V
authors.initials: V
authors.lastname: Favrel
mesh_terms: D000236:Adenoma / Q000532:radiotherapy*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000532:radiotherapy*; D011856:Radiographic Image Enhancement; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome