title: Daily online localization using implanted fiducial markers and its impact on planning target volume for carcinoma prostate.
abstract: BACKGROUND
  Aim of the study was to assess prostate motion on daily basis with respect to setup and to compare the shifts based on bony anatomy and gold fiducial markers.
  
  
  METHODS
  Gold fiducial markers were inserted in prostate under U/S guidance and daily portal images were taken and compared with digitally reconstructed images, both using bony landmarks and fiducial markers as reference. A dose of 2 MU was given for two orthogonal images daily. The mean and standard deviation of displacement using gold seeds and bone were calculated. Systematic and random errors were generated. The planning target volume (PTV) was calculated using the Van Herk formula.
  
  
  RESULTS
  A total of 180 portal images from 10 patients were studied. The mean displacement along x, y and z axes was 1.67 mm, 3.58 mm, and 1.76 mm using fiducial markers and 2.12 mm, 3.47 mm, and 2.09 mm using bony landmarks, respectively. The mean internal organ motion was 1.23 mm (+1.45), 3.11 mm (+2.69 mm); and 1.87 mm (+1.67 mm) along x, y and z axes, respectively. The PTV to account for prostate motion if daily matching was not done was 4.64 mm, 10.41 mm and 4.40 mm along lateral, superoinferior, and anteroposterior directions, respectively. If bony landmarks were used for daily matching, margins of 3.61 mm, 7.31 mm, and 4.72 mm in lateral, superoinferior, and anteroposterior directions should be added to the clinical target volume.
  
  
  CONCLUSIONS
  Daily alignment using gold fiducial markers is an effective method of localizing prostate displacement. It provides the option of reducing margins, thus limiting normal tissue toxicity and allowing the possibility of dose escalation for better long-term control.
authors.affiliation: Batra Cancer Centre, Batra Hospital and Medical Research Centre, Noida, India.
authors.forename: Robin
authors.initials: R
authors.lastname: Khosa
authors.forename: Sapna
authors.initials: S
authors.lastname: Nangia
authors.forename: Kundan S
authors.initials: KS
authors.lastname: Chufal
authors.forename: D
authors.initials: D
authors.lastname: Ghosh
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kaul
authors.forename: Lalit
authors.initials: L
authors.lastname: Sharma
mesh_terms: D006046:Gold / Q000737:chemistry*; D006801:Humans; D008297:Male; D010384:Pelvic Bones / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D011467:Prostate / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D019736:Prostheses and Implants; D011856:Radiographic Image Enhancement; D011880:Radiotherapy Planning, Computer-Assisted
chemical_list: D006046:Gold