title: [Computer-assisted navigation system for interventional CT-guided procedures: results of phantom and clinical studies].
abstract: OBJECTIVE
  To evaluate the technical applicability and accuracy of a navigation system for CT-guided interventional procedures in a phantom and a patient study.
  
  
  METHODS
  A novel navigation tool (CAPPA IRAD, CAS innovations AG, Erlangen, Germany) was employed for CT-guided biopsies in a phantom and in patients. The entire system consists of a PC, navigation software, an optical tracking system and a patient frame. For the phantom study, a spine phantom in wax was used. The phantom as well as the patients were placed on the CT table in a stable position and fixed within a double vacuum device. The patient frame equipped with optical and CT markers was placed above the target region, followed by acquisition of a planning scan. All data were transferred to the navigation system inside the scanning room, and with the aid of the above mentioned navigation software, the biopsy pathway was planned. Hereafter, the needle holder was aligned accordingly, and a coaxial biopsy needle was pushed forward to the planned target. An additional control scan confirmed needle position, and the navigation software was used to evaluate the distance between the target and needle tip.
  
  
  RESULTS
  In the phantom study (n = 60) the average deviation between the planned and documented needle tip position was 1.1 mm. In the clinical study (n = 15), we performed biopsies of the lung, the mediastinal area, the pancreas and liver and some bone biopsies as well as a therapeutic nerve root infiltration. 12 of 15 cases required oblique needle access. In 9 / 15 cases merely a single planning and control scan were required, whereas in 5 / 15 cases additional safety or correction scans were performed. In the case of pancreas biopsy, the lesion (diameter 1 centimeter) visible during the arterial phase only could not be punctured even following repeated corrections due to severe breathing artifacts and pronounced peristaltic movement of the adjacent bowel. The time between planning CT and correct needle position was about 30 minutes.
  
  
  CONCLUSIONS
  The navigation system allows for safe interventions in case of angulated needle access with high accuracy and little tissue trauma. However, insufficient corrections for respiration movement constitute a substantial limitation of the tool.
authors.affiliation: Radiologisches Institut, Friedrich-Alexander Universität Erlangen-Nürnberg, Maximilliansplatz 1, Erlangen. martina.meier-meitinger@uk-erlangen.de
authors.forename: M
authors.initials: M
authors.lastname: Meier-Meitinger
authors.forename: M
authors.initials: M
authors.lastname: Nagel
authors.forename: W
authors.initials: W
authors.lastname: Kalender
authors.forename: W A
authors.initials: WA
authors.lastname: Bautz
authors.forename: U
authors.initials: U
authors.lastname: Baum
mesh_terms: D000772:Anesthesia, Local / Q000295:instrumentation; D016477:Artifacts; D001707:Biopsy, Needle / Q000295:instrumentation; D001842:Bone and Bones / Q000473:pathology; D003287:Contrast Media / Q000008:administration & dosage; D004867:Equipment Design; D004947:Esophagus / Q000473:pathology; D006801:Humans; D008099:Liver / Q000473:pathology; D008168:Lung / Q000473:pathology; D009369:Neoplasms / Q000473:pathology; D010179:Pancreas / Q000473:pathology; D019047:Phantoms, Imaging; D012680:Sensitivity and Specificity; D012984:Software; D013126:Spinal Nerve Roots / Q000187:drug effects; D013131:Spine / Q000473:pathology; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
chemical_list: D003287:Contrast Media