title: Determination of optimum planning target volume margins for various tumor sites using electronic portal imaging.
abstract: OBJECTIVE
  The aim of this study is to evaluate the efficacy of electronic portal imaging (EPI) to measure the set-up errors for four different sites of irradiation caused by patient positioning.
  
  
  METHODS
  A total number of 95 portal images of 11 patients (3 pelvic, 1 total cranium, 3 mantle and 4 tangential fields for breast) were collected during the course of study. The first portal images after a correction of set-up errors according to the simulation films were accepted as the reference images for the subsequent sessions. By matching each portal image with the reference image, the deviations in lateral (x) and superior-inferior (y) axis for all and additionally in antero-posterior (z) axis for pelvis, and standard deviations were calculated.
  
  
  RESULTS
  The set-up errors caused by patient's positioning are completely abolished in 15 mm planning target volume (PTV) margins for all studied cases.
  
  
  CONCLUSIONS
  Standard PTV margins usually completely cover the set-up errors caused by patient's positioning.
authors.affiliation: Department of Radiation Oncology, Ankara University Medical School, Ankara, Turkey. mnalca@medicine.ankara.edu.tr.
authors.forename: M Nalca
authors.initials: MN
authors.lastname: Andrieu
authors.forename: B
authors.initials: B
authors.lastname: Dirican
authors.forename: A Y
authors.initials: AY
authors.lastname: Ozturk
authors.forename: A
authors.initials: A
authors.lastname: Hicsonmez
authors.forename: C
authors.initials: C
authors.lastname: Kurtman
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D018270:Carcinoma, Ductal, Breast / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy; D003131:Combined Modality Therapy; D004582:Electronics, Medical; D016889:Endometrial Neoplasms / Q000473:pathology / Q000532:radiotherapy; D005240:Feasibility Studies; D005260:Female; D006689:Hodgkin Disease / Q000473:pathology / Q000532:radiotherapy; D006801:Humans; D008207:Lymphatic Metastasis / Q000532:radiotherapy; D009369:Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009928:Organ Specificity; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D018714:Radiotherapy, Adjuvant; D012004:Rectal Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery