title: Use of implanted gold fiducial markers with MV-CBCT image-guided IMRT for pancreatic tumours.
abstract: BACKGROUND
  Visualisation of soft tissues such as pancreatic tumours by mega-voltage cone beam CT (MV-CBCT) is frequently difficult and daily localisation is often based on more easily seen adjacent bony anatomy. Fiducial markers implanted into pancreatic tumours serve as surrogates for tumour position and may more accurately represent absolute tumour position. Differences in daily shifts based on alignment to implanted fiducial markers vs. alignment to adjacent bony anatomy were compared.
  
  
  METHODS
  Gold fiducial markers were placed into the pancreatic tumour under endoscopic ultrasound (EUS) guidance in 12 patients. Patients subsequently received image-guided intensity-modulated radiation therapy (IG-IMRT). MV-CBCT was performed prior to each fraction and isocentre shifts were performed based on alignment to the fiducial markers. We retrospectively reviewed archived MV-CBCT datasets and calculated shift differences in the left-right (LR), superior-inferior (SI) and anterior-posterior (AP) axes relative to shifts based on alignment to adjacent bony anatomy.
  
  
  RESULTS
  Two hundred forty-three fractions were analysed. The mean absolute difference in isocentre shifts between the fiducial markers and those aligned to bony anatomy was 3.4 mm (range 0-13 mm), 6.3 mm (range 0-21 mm) and 2.6 mm (range 0-12 mm), in LR, SI and AP directions, respectively. The mean three-dimensional vector shift difference between markers vs. bony anatomy alignment was 8.6 mm.
  
  
  CONCLUSIONS
  These data suggest that fiducial markers used in conjunction with MV-CBCT improve the accuracy of daily target delineation compared with localisation using adjacent bony anatomy and that gold fiducial markers using MV-CBCT alignment are a viable option for target localisation during IG-IMRT.
authors.affiliation: Department of Radiation Oncology, Lemmen-Holton Cancer Pavilion, Spectrum Health, Grand Rapids, Michigan, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Packard
authors.affiliation: Department of Radiation Oncology, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, Pennsylvania, USA.
authors.forename: Olivier
authors.initials: O
authors.lastname: Gayou
authors.affiliation: Center for Digestive Health, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, Pennsylvania, USA.
authors.forename: Krishna
authors.initials: K
authors.lastname: Gurram
authors.affiliation: Department of Radiation Oncology, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, Pennsylvania, USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Weiss
authors.affiliation: Center for Digestive Health, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, Pennsylvania, USA.
authors.forename: Shyam
authors.initials: S
authors.lastname: Thakkar
authors.affiliation: Department of Radiation Oncology, Allegheny General Hospital, Allegheny Health Network, Pittsburgh, Pennsylvania, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Kirichenko
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D057918:Fiducial Markers; D006046:Gold; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
chemical_list: D006046:Gold
keywords: IMRT; fiducial marker; image-guidance; pancreatic cancer; target motion