title: Insertion and fixation of fiducial markers for setup and tracking of lung tumors in radiotherapy.
abstract: OBJECTIVE
  Internal 1.5-mm fiducial markers were used in real-time tumor-tracking radiotherapy (RT) for lung cancer. The fixation rate of the markers using the bronchial insertion technique, reliability of the setup using markers around the target volume, dislocation of the markers after real-time tumor-tracking RT, and long-term toxicity of marker insertion were investigated.
  
  
  METHODS
  Between July 2000 and April 2004, 154 gold markers were inserted into 57 patients with peripheral lung cancer. The distances between the implanted markers in 198 measurements in 71 set-ups in 11 patients were measured using two sets of orthogonal diagnostic X-ray images of the real-time tumor-tracking RT system. The distance between the markers and the chest wall was also measured in a transaxial CT image on 186 occasions in 48 patients during treatment planning and during follow-up. The median treatment time was 6 days (range, 4-14 days).
  
  
  RESULTS
  In 115 (75%) of the 154 inserted markers, the gold marker was detected throughout the treatment period. In 122 markers detected at CT planning, 115 (94%) were detected until the end of treatment. The variation in the distances between the implanted markers was within +/-2 mm in 95% and +/-1 mm in 80% during treatment. The variation in the distances between the implanted markers was >2 mm in at least one direction in 9% of the setups for which reexamination with a CT scan was indicated. The fixation rate in the left upper lobe was lower than in the other lobes. A statistically significant relationship was found between a shorter distance between the markers and the chest wall and the fixation rate, suggesting that the markers in the smaller bronchial lumens fixed better than those in the larger lumens. A learning curve among the endoscopists was suggested in the fixation rate. The distance between the markers and the chest wall changed significantly within a median of 44 days (range, 16-181 days) after treatment.
  
  
  CONCLUSIONS
  The fixation of markers into the bronchial tree was useful for the setup for peripheral lung cancer and had an accuracy of +/-2 mm during the 1-2-week treatment period. The relationship between the markers and tumor can change significantly after 2 weeks, suggesting that adaptive four-dimensional RT is required.
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
authors.forename: Mikado
authors.initials: M
authors.lastname: Imura
authors.forename: Koichi
authors.initials: K
authors.lastname: Yamazaki
authors.forename: Hiroki
authors.initials: H
authors.lastname: Shirato
authors.forename: Rikiya
authors.initials: R
authors.lastname: Onimaru
authors.forename: Masaharu
authors.initials: M
authors.lastname: Fujino
authors.forename: Shinichi
authors.initials: S
authors.lastname: Shimizu
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Harada
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Ogura
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Dosaka-Akita
authors.forename: Kazuo
authors.initials: K
authors.lastname: Miyasaka
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001980:Bronchi; D005260:Female; D006046:Gold; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D006046:Gold