title: Implantation and stability of metallic fiducials within pulmonary lesions.
abstract: OBJECTIVE
  To report and describe implantation techniques and stability of metallic fiducials in lung lesions to be treated with external beam radiotherapy.
  
  
  METHODS
  Patients undergoing radiation therapy for small early-stage lung cancer underwent implantation with small metallic markers. Implantation was either transcutaneous under computed tomographic (CT) or fluoroscopic guidance or transbronchial with the superDimension/Bronchus system (radiofrequency signal-based bronchoscopy guidance related to CT images).
  
  
  RESULTS
  Implantation was performed transcutaneously in 15 patients and transbronchially in 8 patients. Pneumothorax occurred with eight of the 15 transcutaneous implants, six of which required chest tube placement. None of the patients who underwent transbronchial implantation developed pneumothorax. Successfully inserted markers were all usable during gated image-guided radiotherapy. Marker stability was determined by observing the variation in gross target volume (GTV) centroid relative to the marker on repeated CT scans. Average three-dimensional variation in the GTV center relative to the marker was 2.6 +/- 1.3 (SD) mm, and the largest variation along any anatomic axis for any patient was <5 mm. Average GTV volume decrease during the observation period was 34% +/- 23%. Gross tumor volumes do not appear to shrink uniformly about the center of the tumor, but rather the tumor shapes deform substantially throughout treatment.
  
  
  CONCLUSIONS
  Transbronchial marker placement is less invasive than transcutaneous placement, which is associated with high pneumothorax rates. Although marker geometry can be affected by tumor shrinkage, implanted markers are stable within tumors throughout the treatment duration regardless of implantation method.
authors.affiliation: Department of Radiation Oncology, M. D. Anderson Cancer Center Orlando, Orlando, FL 32806, USA. patrick.kupelian@orhs.org
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Kupelian
authors.forename: Alan
authors.initials: A
authors.lastname: Forbes
authors.forename: Twyla R
authors.initials: TR
authors.lastname: Willoughby
authors.forename: Karen
authors.initials: K
authors.lastname: Wallace
authors.forename: Rafael R
authors.initials: RR
authors.lastname: Mañon
authors.forename: Sanford L
authors.initials: SL
authors.lastname: Meeks
authors.forename: Luis
authors.initials: L
authors.lastname: Herrera
authors.forename: Alan
authors.initials: A
authors.lastname: Johnston
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Herran
mesh_terms: D001999:Bronchoscopy / Q000379:methods*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D015505:Chest Tubes; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011030:Pneumothorax / Q000209:etiology / Q000628:therapy; D019736:Prostheses and Implants / Q000009:adverse effects; D015641:Radiography, Interventional / Q000379:methods*; D014057:Tomography, X-Ray Computed