title: Image overlay for CT-guided needle insertions.
abstract: OBJECTIVE
  We present a 2D image overlay device to assist needle placement on computed tomography (CT) scanners.
  
  
  METHODS
  The system consists of a flat display and a semitransparent mirror mounted on the gantry. When the physician looks at the patient through the mirror, the CT image appears to be floating inside the body with correct size and position as if the physician had 2D 'X-ray vision'. The physician draws the optimal path on the CT image. The composite image is rendered on the display and thus reflected in the mirror. The reflected image is used to guide the physician in the procedure. In this article, we describe the design and various embodiments of the 2D image overlay system, followed by the results of phantom and cadaver experiments in multiple clinical applications.
  
  
  RESULTS
  Multiple skeletal targets were successfully accessed with one insertion attempt. Generally, successful access was recorded on liver targets when a clear path opened, but the number of attempts and accuracy showed variability because of occasional lack of access. Soft tissue deformation further reduced the accuracy and consistency in comparison to skeletal targets.
  
  
  CONCLUSIONS
  The system demonstrated strong potential for reducing faulty needle insertion attempts, thereby reducing X-ray dose and patient discomfort.
authors.affiliation: Johns Hopkins University, Baltimore, MD 21218-2682, USA. gabor@cs.jhu.edu
authors.forename: Gabor
authors.initials: G
authors.lastname: Fichtinger
authors.forename: Anton
authors.initials: A
authors.lastname: Deguet
authors.forename: Gregory
authors.initials: G
authors.lastname: Fischer
authors.forename: Iulian
authors.initials: I
authors.lastname: Iordachita
authors.forename: Emese
authors.initials: E
authors.lastname: Balogh
authors.forename: Ken
authors.initials: K
authors.lastname: Masamune
authors.forename: Russell H
authors.initials: RH
authors.lastname: Taylor
authors.forename: Laura M
authors.initials: LM
authors.lastname: Fayad
authors.forename: Michelle
authors.initials: M
authors.lastname: de Oliveira
authors.forename: S James
authors.initials: SJ
authors.lastname: Zinreich
mesh_terms: D000818:Animals; D001707:Biopsy, Needle; D002102:Cadaver; D002138:Calibration; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019047:Phantoms, Imaging; D015641:Radiography, Interventional / Q000295:instrumentation*; D013552:Swine; D014057:Tomography, X-Ray Computed; D014584:User-Computer Interface