title: Clinical utility of real-time fusion guidance for biopsy and ablation.
abstract: OBJECTIVE
  To show utility, accuracy, and clinical outcomes of electromagnetic tracking and multimodality image fusion for guidance of biopsy and radiofrequency (RF) ablation procedures.
  
  
  METHODS
  A combination of conventional image guidance (ultrasound[US]/computed tomography [CT]) and a research navigation system was used in 40 patients undergoing biopsy or RF ablation to assist in target localization and needle and electrode placement. The navigation system displays electromagnetically tracked needles and US images relative to a preprocedural CT scan. Additional images (prior positron emission tomography [PET] or magnetic resonance [MR] imaging) can be fused with CT as needed. Needle aiming with and without tracking were compared, the utility of navigation for each procedure was assessed, the system's off-target tracking error for two different registration methods was evaluated, and setup time was recorded.
  
  
  RESULTS
  The tracking error could be evaluated in 35 of 40 patients. A basic tracking error of 3.8 mm ± 2.3 was shown using skin fiducial markers for registration. The error improved to 2.7 mm ± 1.6 when using prior internal needle positions as additional fiducial markers. Real-time fusion of US with CT and registration with prior PET and MR imaging were successful and provided clinically relevant guidance information, enabling 19 of the 40 procedures.
  
  
  CONCLUSIONS
  The spatial accuracy of the navigation system is sufficient to display clinically relevant image guidance information during biopsy and RF ablation. Breath holding and respiratory gating are effective in minimizing the error associated with tissue motion. In 48% of cases, the navigation system provided information crucial for successful execution of the procedure. Fusion of real-time US with CT or prior diagnostic images may enable procedures that are not feasible with standard, single-modality image guidance.
authors.affiliation: Philips Research North America, Briarcliff Manor, New York, USA. jochen.kruecker@philips.com
authors.forename: Jochen
authors.initials: J
authors.lastname: Krücker
authors.forename: Sheng
authors.initials: S
authors.lastname: Xu
authors.forename: Aradhana
authors.initials: A
authors.lastname: Venkatesan
authors.forename: Julia K
authors.initials: JK
authors.lastname: Locklin
authors.forename: Hayet
authors.initials: H
authors.lastname: Amalou
authors.forename: Neil
authors.initials: N
authors.lastname: Glossop
authors.forename: Bradford J
authors.initials: BJ
authors.lastname: Wood
mesh_terms: D000328:Adult; D000368:Aged; D001707:Biopsy, Needle / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods*; D055590:Electromagnetic Phenomena; D005260:Female; D057918:Fiducial Markers; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis / Q000601:surgery*; D008113:Liver Neoplasms / Q000175:diagnosis / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D015641:Radiography, Interventional / Q000379:methods*; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed; D018084:Ultrasonography, Interventional