title: Is it essential to use fiducial markers during cone-beam CT-based radiotherapy for prostate cancer patients?
abstract: OBJECTIVE
  To compare soft-tissue cone-beam computed tomography (CBCT-P) and fiducial marker (CBCT-FM)-based image guided radiotherapy in prostate cancer patients.
  
  
  METHODS
  Sixteen prostate cancer patients were treated with volumetric modulated arc therapy. Manual alignment using CBCT-P and CBCT-FM was performed for each patient. Couch shifts were calculated and compared between methods in the left-right (x), superior-inferior (y), and anterior-posterior (z) directions.
  
  
  RESULTS
  CBCT-P and CBCT-FM alignments were compared using 252 scans from the 16 patients. Mean displacement from zero was 2.4 ± 1.3, 1.7 ± 1.2, and 1.8 ± 1.1 mm for CBCT-P and 2.3 ± 1.3, 1.7 ± 1.1 and 1.8 ± 1.1 mm for CBCT-FM in the x, y and z directions, respectively. There was no difference in median displacement between CBCT-P and CBCT-FM; however, there was a significant positive correlation between CBCT-P- and CBCT-FM-based displacements in the x (r = 0.881; p < 0.001), y (r = 0.789; p < 0.001) and z (r = 0.856; p < 0.001) directions by linear regression analysis. Systematic deviations within each group were <1 mm; however, random and systematic errors were similar in the x and y directions but larger in the z direction.
  
  
  CONCLUSIONS
  Our study demonstrated that CBCT-FM was not superior to CBCT-P for image-guided radiotherapy in prostate cancer patients.
authors.affiliation: Department of Radiation Oncology, Baskent University Faculty of Medicine, 01120, Adana, Turkey.
authors.forename: Berna A
authors.initials: BA
authors.lastname: Yildirim
authors.affiliation: Department of Radiation Oncology, Baskent University Faculty of Medicine, 01120, Adana, Turkey. hcemonal@hotmail.com.
authors.forename: Cem
authors.identifier: http://orcid.org/0000-0002-2742-9021
authors.initials: C
authors.lastname: Onal
authors.affiliation: Department of Radiation Oncology, Baskent University Faculty of Medicine, 01120, Adana, Turkey.
authors.forename: Yemliha
authors.initials: Y
authors.lastname: Dolek
mesh_terms: D000368:Aged; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D057918:Fiducial Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D015641:Radiography, Interventional / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods
keywords: Cone-beam CT; Fiducial marker; Image-guided radiotherapy; Prostate cancer; Setup errors