title: An electromagnetic navigation system for transbronchial interventions with a novel approach to respiratory motion compensation.
abstract: OBJECTIVE
  Bronchoscopic interventions, such as transbronchial needle aspiration (TBNA), are commonly performed procedures to diagnose and stage lung cancer. However, due to the complex structure of the lung, one of the main challenges is to find the exact position to perform a biopsy and to actually hit the biopsy target (e.g., a lesion). Today, most interventions are accompanied by fluoroscopy to verify the position of the biopsy instrument, which means additional radiation exposure for the patient and the medical staff. Furthermore, the diagnostic yield of TBNA is particularly low for peripheral lesions.
  
  
  METHODS
  To overcome these problems the authors developed an image-guided, electromagnetic navigation system for transbronchial interventions. The system provides real time positioning information for the bronchoscope and a transbronchial biopsy instrument with only one preoperatively acquired computed tomography image. A twofold respiratory motion compensation method based on a particle filtering approach allows for guidance through the entire respiratory cycle. In order to evaluate our system, 18 transbronchial interventions were performed in seven ventilated swine lungs using a thorax phantom.
  
  
  RESULTS
  All tracked bronchoscope positions were corrected to the inside of the tracheobronchial tree and 80.2% matched the correct bronchus. During regular respiratory motion, the mean overall targeting error for bronchoscope tracking and TBNA needle tracking was with compensation on 10.4 ± 1.7 and 10.8 ± 3.0 mm, compared to 14.4 ± 1.9 and 13.3 ± 2.7 mm with compensation off. The mean fiducial registration error (FRE) was 4.2 ± 1.1 mm.
  
  
  CONCLUSIONS
  The navigation system with the proposed respiratory motion compensation method allows for real time guidance during bronchoscopic interventions, and thus could increase the diagnostic yield of transbronchial biopsy.
authors.affiliation: Division of Medical and Biological Informatics, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany. i.gergel@dkfz-heidelberg.de
authors.forename: Ingmar
authors.initials: I
authors.lastname: Gergel
authors.forename: Jan
authors.initials: J
authors.lastname: Hering
authors.forename: Ralf
authors.initials: R
authors.lastname: Tetzlaff
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Meinzer
authors.forename: Ingmar
authors.initials: I
authors.lastname: Wegner
mesh_terms: D016477:Artifacts; D020680:Bronchoscopes; D004581:Electronics / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D008280:Magnetics / Q000295:instrumentation*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000295:instrumentation*; D012680:Sensitivity and Specificity