title: Freehand biopsy guided by electromagnetic needle tracking: a phantom study.
abstract: OBJECTIVE
  To evaluate the overall accuracy and time spent on biopsy guided by electromagnetic needle tracking in a phantom compared with the standard technique of US-guided biopsy with an attached steering device. Furthermore, to evaluate off-plane biopsy guided by needle tracking.
  
  
  METHODS
  Three different series of biopsy were performed in a phantom: one with a steering device attached to the transducer without needle tracking, simulating the standard ultrasound-guided biopsy procedure (series 1), one freehand in the scan plane using electromagnetic needle tracking (series 2), and one freehand off-the-scan plane using electromagnetic needle tracking (series 3). The phantom contained spheres of 1  cm in diameter filled with red dye. Each time of the phantom surface was perforated counted as an attempt.
  
  
  RESULTS
  180 biopsies were performed. The mean time spent on each biopsy in series one was 19.9 seconds (SD: 9.1), in series two 34.1 seconds (SD: 17.9) and in series three 34.4 seconds (SD: 14.0). The overall rate of success was: 88 % for in-plane needle-guided biopsy, 87 % for in-plane needle tracking, and 92 % for off-plane needle tracking. No statistically significant difference between the methods was shown.
  
  
  CONCLUSIONS
  Needle navigation is a potentially valuable tool for image-guided biopsy with an equal rate of success compared with conventional image-guided biopsy. Furthermore, it enables off-plane image-guided biopsy.
authors.affiliation: Department of Radiology, Copenhagen University Hospital, Rigshospitalet, Denmark. caroline.ewertsen@dadlnet.dk
authors.forename: C
authors.initials: C
authors.lastname: Ewertsen
authors.forename: K Rue
authors.initials: KR
authors.lastname: Nielsen
authors.forename: M Bachmann
authors.initials: MB
authors.lastname: Nielsen
mesh_terms: D001707:Biopsy, Needle / Q000295:instrumentation*; D004526:Efficiency; D055590:Electromagnetic Phenomena; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation*; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D012984:Software; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D014159:Transducers; D018084:Ultrasonography, Interventional / Q000295:instrumentation*