While magnetic resonance imaging has made great strides in other areas of body imaging, it is not the modality of choice where the airways of the lung is concerned because of artifacts which occur at air-water interfaces. X-ray CT remains the modality of choice for imaging the trachea. The introduction of Helical (or Spiral) CT along with the increased use of Electron Beam CT has is provided the speeds of scanning needed to acquire volumetric image data sets in a single or a few breath holds. Using the patient scan data and our software, VIDA, we have developed methodologies to volumetrically visualize the primary bronchial tree and associated external structures of interest and to quantitate the airway luminal geometry. To quantitate the airway luminal geometry, we have developed a method of identifying the airway center-line which then allows us to re-slice the airway such that slices are selected to be perpendicular to the local airway long axis. These new slices allow us to then utilize objective methods for identifying the airway boarders and to report true cross sectional area of the area as a function of distance along the airway. This digital x-ray CT based assessment of the airway can be done without the discomfort of the bronchoscopy procedure and without the risks associated with bronchoscopy. Through a non-invasive assessment of the airway prior to bronchoscopic intervention, the bronchoscopist is able to better prepare for the required procedure and to perform interventions which might otherwise not have been contemplated.

While volumetric imaging of the airways along with associated quantitative assessments date back 15-18 years to the earliest days of the Mayo Dynamic Spatial Reconstructor project, recently it has become of interest to display the volumetric images with the viewer's perspective placed inside the lumen rather than displaying the airway lumen as a solid three-dimensional structure. The internal view of the airway simulates the view seen by the conventional bronchoscope and has been dubbed "Virtual Bronchoscopy." Efforts are underway to link the CT-based Virtual images with the actual bronchoscopic images during the bronchoscopic procedure to provide the experienced bronchoscopist with additional information leading to successful biopsies of suspected mediastinal tumors. The linkage between the virtual and the actual bronchoscopic image is expected to also provide the less experienced bronchoscopist with a road map of the often confusing airway tree structure.