title: Feasibility of electromagnetic transponder use to monitor inter- and intrafractional motion in locally advanced pancreatic cancer patients.
abstract: OBJECTIVE
  The primary objective of this study was to determine the feasibility of electromagnetic transponder implantation in patients with locally advanced unresectable pancreatic cancer. Secondarily, the use of transponders to monitor inter- and intrafractional motion, and the efficacy of breath holding for limiting target motion, were examined.
  
  
  METHODS
  During routine screening laparoscopy, 5 patients without metastatic disease were implanted with transponders peri-tumorally. The Calypso System's localization and tracking modes were used to monitor inter- and intrafractional motion, respectively. Intrafractional motion, with and without breath holding, was also examined using Calypso tracking mode.
  
  
  RESULTS
  Transponder implantation was well tolerated in all patients, with minimal migration, aside from 1 patient who expulsed a single transponder. Interfractional motion based on mean shifts from setup using tattoos/orthogonal imaging to transponder based localization from 164 treatments was significant in all dimensions. Mean shift (in millimeters), followed by the standard deviation and p value, were as follows: X-axis: 4.5 mm (1.0, p = 0.01); Y axis: 6.4 mm (1.9, p = 0.03); and Z-axis 3.9 mm (0.6, p = 0.002). Mean intrafractional motion was also found to be significant in all directions: superior, 7.2 mm (0.9, p = 0.01); inferior, 11.9 mm (0.9, p < 0.01); anterior: 4.9 mm (0.5, p = 0.01); posterior, 2.9 mm (0.5, p = 0.02); left, 2.2 mm (0.4, p = 0.02); and right, 3.1 mm (0.6, p = 0.04). Breath holding during treatment significantly decreased tumor motion in all directions.
  
  
  CONCLUSIONS
  Electromagnetic transponder implantation appears to be safe and effective for monitoring inter- and intrafractional motion. Based on these results a larger clinical trial is underway.
authors.affiliation: Department of Radiation Oncology, The Vanderbilt Clinic, Nashville, TN 37232e5671, USA. eric.t.shinohara@vanderbilt.edu
authors.forename: Eric T
authors.initials: ET
authors.lastname: Shinohara
authors.forename: Alireza
authors.initials: A
authors.lastname: Kassaee
authors.forename: Nandita
authors.initials: N
authors.lastname: Mitra
authors.forename: Neha
authors.initials: N
authors.lastname: Vapiwala
authors.forename: John P
authors.initials: JP
authors.lastname: Plastaras
authors.forename: Jeff
authors.initials: J
authors.lastname: Drebin
authors.forename: Fei
authors.initials: F
authors.lastname: Wan
authors.forename: James M
authors.initials: JM
authors.lastname: Metz
mesh_terms: D059925:Anatomic Landmarks; D019583:Dose Fractionation, Radiation; D004574:Electromagnetic Fields; D005240:Feasibility Studies; D057918:Fiducial Markers; D006801:Humans; D009068:Movement; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D019736:Prostheses and Implants; D020266:Radiotherapy, Conformal / Q000379:methods; D012119:Respiration; D014057:Tomography, X-Ray Computed / Q000379:methods