title: Assessment with cone-beam computed tomography of intrafractional motion and interfractional position changes of resectable and borderline resectable pancreatic tumours with implanted fiducial marker.
abstract: OBJECTIVE
  The volume of targets to which a high radiation dose can be delivered is limited for pancreatic radiotherapy. We assessed changes in movements of pancreatic tumours between simulation and treatment and determined compensatory margins.
  
  
  METHODS
  For 23 patients, differences in implanted fiducial marker motion magnitude (MMM) and mean marker position (MMP) between four-dimensional CT and cone-beam CT were measured. Subsequently, residual uncertainty was simulated after no action level (NAL) and extended no action level (eNAL) protocols were adopted.
  
  
  RESULTS
  With no correction, respective 95th percentile of MMM were 4.5 mm, 6.2 mm and 16.0 mm and systematic (random) errors of MMP were 2.8 mm (3.3 mm), 3.2 mm (2.0 mm) and 5.9 mm (4.0 mm) in the left-right (L-R), anteroposterior (A-P) and superoinferior (S-I) directions, so that large margins were required (L-R, 10.5 mm; A-P, 11.7 mm; and S-I, 24.8 mm). NAL reduced systematic errors of MMP, but resultant margins remained large (L-R, 8.0 mm; A-P, 9.6 mm; and S-I, 18.1 mm). eNAL compensated for time trends and obtained minimal margins (L-R, 6.7 mm; A-P, 6.7 mm; and S-I, 15.2 mm).
  
  
  CONCLUSIONS
  Motion magnitude and position of pancreatic tumours during simulation are frequently not representative of that during treatment. eNAL compensated for systematic interfractional position change and would be a practical approach for improving targeting accuracy. Advances in knowledge: Considerably large margins, especially in the S-I direction, were required to compensate for intrafractional motion and interfractional position changes of the pancreatic tumour. An application of eNAL was an effective strategy to diminish these margins.
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.|2 Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Ohira
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Isono
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.|3 Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ueda
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Takero
authors.initials: T
authors.lastname: Hirata
authors.affiliation: 4 Department of Cancer survey and gastrointestinal oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Reiko
authors.initials: R
authors.lastname: Ashida
authors.affiliation: 5 Department of Surgery, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Miyazaki
authors.affiliation: 2 Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takashina
authors.affiliation: 2 Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Koizumi
authors.affiliation: 1 Department of Radiation Oncology, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.
authors.forename: Teruki
authors.initials: T
authors.lastname: Teshima
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D057918:Fiducial Markers; D056973:Four-Dimensional Computed Tomography; D006801:Humans; D008297:Male; D009038:Motion; D010179:Pancreas / Q000000981:diagnostic imaging; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results