title: Interfractional positional variability of fiducial markers and primary tumors in locally advanced non-small-cell lung cancer during audiovisual biofeedback radiotherapy.
abstract: OBJECTIVE
  To evaluate implanted markers as a surrogate for tumor-based setup during image-guided lung cancer radiotherapy with audiovisual biofeedback.
  
  
  METHODS
  Seven patients with locally advanced non-small-cell lung cancer were implanted bronchoscopically with gold coils. Markers, tumor, and a reference bony structure (vertebra) were contoured for all 10 phases of the four-dimensional respiration-correlated fan-beam computed tomography and weekly four-dimensional cone-beam computed tomography.
  
  
  RESULTS
  The systematic/random interfractional marker-to-tumor centroid displacements were 2/3, 2/2, and 3/3 mm in the x (lateral), y (anterior-posterior), and z (superior-inferior) directions, respectively. The systematic/random interfractional marker-to-bone displacements were 2/3, 2/3, and 2/3 mm in the x, y, and z directions, respectively. The systematic/random tumor-to-bone displacements were 2/3, 2/4, and 4/4 mm in the x, y, and z directions, respectively. All displacements changed significantly over time (p < 0.0001).
  
  
  CONCLUSIONS
  Although marker-based image guidance may decrease the risk for geometric miss compared with bony anatomy-based positioning, the observed displacements between markers and tumor centroids indicate the need for repeated soft tissue imaging, particularly in situations with large tumor volume change and large initial marker-to-tumor centroid distance.
authors.affiliation: Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, USA. nroman@mcvh-vcu.edu
authors.forename: Nicholas O
authors.initials: NO
authors.lastname: Roman
authors.forename: Wes
authors.initials: W
authors.lastname: Shepherd
authors.forename: Nitai
authors.initials: N
authors.lastname: Mukhopadhyay
authors.forename: Geoffrey D
authors.initials: GD
authors.lastname: Hugo
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Weiss
mesh_terms: D000368:Aged; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D059248:Chemoradiotherapy / Q000379:methods; D054893:Cone-Beam Computed Tomography / Q000379:methods; D019583:Dose Fractionation, Radiation; D005260:Female; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006046:Gold; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D047368:Tumor Burden
chemical_list: D006046:Gold