title: Three-dimensional ultrasound-based navigation combined with preoperative CT during abdominal interventions: a feasibility study.
abstract: OBJECTIVE
  Three-dimensional (3D) intraoperative ultrasound may be easier to interpret when used in combination with less noisy preoperative image data such as CT. The purpose of this study was to evaluate the use of preoperative image data in a 3D ultrasound-based navigation system specially designed for minimally invasive abdominal surgery. A prototype system has been tested in patients with aortic aneurysms undergoing clinical assessment before and after abdominal aortic stent-graft implantation.
  
  
  METHODS
  All patients were first imaged by spiral CT followed by 3D ultrasound scanning. The CT volume was registered to the patient using fiducial markers. This enabled us to compare corresponding slices from 3D ultrasound and CT volumes. The accuracy of the patient registration was evaluated both using the external fiducial markers (artificial landmarks glued on the patient's skin) and using intraoperative 3D ultrasound as a measure of the true positioning of anatomic landmarks inside the body.
  
  
  RESULTS
  The mean registration accuracy on the surface was found to be 7.1 mm, but increased to 13.0 mm for specific landmarks inside the body. CT and ultrasound gave supplementary information of surrounding structures and position of the patient's anatomy. Fine-tuning the initial patient registration of the CT data with a multimodal CT to intraoperative 3D ultrasound registration (e.g., mutual information), as well as ensuring no movements between this registration and image guidance, may improve the registration accuracy.
  
  
  CONCLUSIONS
  Preoperative CT in combination with 3D ultrasound might be helpful for guiding minimal invasive abdominal interventions.
authors.affiliation: Ultrasound Department, SINTEF Unimed, N-7465 Trondheim, Norway. jonk@sintef.no
authors.forename: J H
authors.initials: JH
authors.lastname: Kaspersen
authors.forename: E
authors.initials: E
authors.lastname: Sjølie
authors.forename: J
authors.initials: J
authors.lastname: Wesche
authors.forename: J
authors.initials: J
authors.lastname: Asland
authors.forename: J
authors.initials: J
authors.lastname: Lundbom
authors.forename: A
authors.initials: A
authors.lastname: Odegård
authors.forename: F
authors.initials: F
authors.lastname: Lindseth
authors.forename: T A
authors.initials: TA
authors.lastname: Nagelhus Hernes
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000601:surgery; D005240:Feasibility Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007430:Intraoperative Care; D019060:Minimally Invasive Surgical Procedures; D011300:Preoperative Care; D014057:Tomography, X-Ray Computed; D018084:Ultrasonography, Interventional