title: The role of surgical clips in the evaluation of interfractional uncertainty for treatment of hepatobiliary and pancreatic cancer with postoperative radiotherapy.
abstract: OBJECTIVE
  To evaluate the utility of implanted surgical clips for detecting interfractional errors in the treatment of hepatobiliary and pancreatic cancer with postoperative radiotherapy (PORT).
  
  
  METHODS
  Twenty patients had been treated with PORT for locally advanced hepatobiliary or pancreatic cancer, from November 2014 to April 2016. Patients underwent computed tomography simulation and were treated in expiratory breathing phase. During treatment, orthogonal kilovoltage (kV) imaging was taken twice a week, and isocenter shifts were made to match bony anatomy. The difference in position of clips between kV images and digitally reconstructed radiographs was determined. Clips were consist of 3 proximal clips (clip_p, ≤2 cm) and 3 distal clips (clip_d, >2 cm), which were classified according to distance from treatment center. The interfractional displacements of clips were measured in the superior-inferior (SI), anterior-posterior (AP), and right-left (RL) directions.
  
  
  RESULTS
  The translocation of clip was well correlated with diaphragm movement in 90.4% (190/210) of all images. The clip position errors greater than 5 mm were observed in 26.0% in SI, 1.8% in AP, and 5.4% in RL directions, respectively. Moreover, the clip position errors greater than 10 mm were observed in 1.9% in SI, 0.2% in AP, and 0.2% in RL directions, despite respiratory control.
  
  
  CONCLUSIONS
  Quantitative analysis of surgical clip displacement reflect respiratory motion, setup errors and postoperative change of intraabdominal organ position. Furthermore, position of clips is distinguished easily in verification images. The identification of the surgical clip position may lead to a significant improvement in the accuracy of upper abdominal radiation therapy.
authors.affiliation: Department of Radiation Oncology, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Jin Suk
authors.initials: JS
authors.lastname: Bae
authors.affiliation: Department of Radiation Oncology, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.|Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Dong Hyun
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.|Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Won Taek
authors.initials: WT
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Yong Ho
authors.initials: YH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.|Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Dahl
authors.initials: D
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.|Biomedical Research Institute, Pusan National University Hospital, Pusan National University School of Medicine, Busan, Korea.
authors.forename: Yong Kan
authors.initials: YK
authors.lastname: Ki
keywords: Clip; Hepatobiliary cancer; Interfractional error; Pancreatic cancer; Postoperative radiotherapy