title: Electromagnetic navigational bronchoscopy-guided fiducial markers for lung stereotactic body radiation therapy: analysis of safety, feasibility, and interfraction stability.
abstract: BACKGROUND
  Embolization coils as fiducial markers for pulmonary stereotactic body radiation therapy (SBRT) are perceived to be the optimal marker type, given their ability to conform and anchor within the small airways. The aim of our study was to assess retention, placement, migration, feasibility, and safety of electromagnetic navigational bronchoscopy (ENB)-guided embolization coil markers throughout courses of SBRT.
  
  
  METHODS
  Thirty-one patients with 34 nodules underwent ENB-guided fiducial placement of several 4 mm fibered platinum embolization coils before SBRT. Patient and nodule positioning was confirmed with daily pretreatment cone-beam computed tomography (CBCT). Fiducial positional characteristics were analyzed utilizing radiation treatment-planning software comparing the simulation CT with daily CBCTs.
  
  
  RESULTS
  Of 105 fiducials placed, 103 were identifiable on simulation CT (retention rate: 98.1%). Incidence of asymptomatic pneumothoraces was 6%. One patient experienced hemoptysis requiring hospitalization. Eighty-six percent of fiducials were placed within 1 cm of the nodule, with 52% of fiducials placed directly on the nodule surface. Throughout a 5-fraction SBRT course, fiducial displacement was <7, 5, and 2 mm in 98%, 96%, and 67% of pretreatment CBCTs.
  
  
  CONCLUSIONS
  ENB placement of embolization coils as fiducials for lung SBRT image guidance is associated with a low rate of iatrogenic pneumothoraces, and resulted in reliable placement of the fiducials in close proximity to the lung nodule. Embolization coils retained their relative position to the nodule throughout the course of SBRT, and provide an excellent alternative to linear gold seeds.
authors.affiliation: *Department of Radiation Medicine †Division of Pulmonary and Critical Care Medicine, Oregon Health and Science University ‡Pulmonary and Critical Care Medicine, Department of Veterans Affairs Medical Center, Portland, OR.
authors.forename: Nima
authors.initials: N
authors.lastname: Nabavizadeh
authors.forename: Junan
authors.initials: J
authors.lastname: Zhang
authors.forename: David A
authors.initials: DA
authors.lastname: Elliott
authors.forename: James A
authors.initials: JA
authors.lastname: Tanyi
authors.forename: Charles R
authors.initials: CR
authors.lastname: Thomas
authors.forename: Martin
authors.initials: M
authors.lastname: Fuss
authors.forename: Mark
authors.initials: M
authors.lastname: Deffebach
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001999:Bronchoscopy / Q000379:methods*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000601:surgery*; D004621:Embolization, Therapeutic / Q000295:instrumentation; D004867:Equipment Design; D005240:Feasibility Studies; D057918:Fiducial Markers; D005548:Foreign-Body Migration / Q000453:epidemiology; D006801:Humans; D061705:Image-Guided Biopsy; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D059346:Magnets; D008875:Middle Aged; D011030:Pneumothorax / Q000453:epidemiology / Q000209:etiology; D011300:Preoperative Care / Q000379:methods; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed