Technical Note. 3D Virtual Endoscopy of the Upper Airway: Optimization of the Scan Parameters in a Cadaver Phantom and Clinical Assessment

Abstract

Our goal was to evaluate the influence of the scan parameters on the 3D virtual endoscopy of the larynx and trachea and the clinical assessment. Helical CT (HiSpeed Advantage; GE, Milwaukee, WI, U.S.A.) of a cadaver phantom was performed with increased collimation (1-10 mm) and pitch (0.5-3). Seventy-two patients with complaints of the upper airways were investigated by virtual endoscopy and their results were compared with the findings of regular endoscopy. Best correlation between virtual endoscopy and anatomical findings, diagnostic quality of the axial slices, and useful longitudinal coverage of the examination were obtained with a collimation of 3 mm and a pitch of 1.5. Space-occupying tumors and stenosis were detected correctly, but the mucous membrane could not be visualized. 3D virtual endoscopy proved to be a valuable method for displaying anatomical structures. For an optimal protocol, a collimation of 3 mm with a pitch of 1.5 is recommended.

Virtual tools for imaging of the thorax

“…All space occupying tumours w5 mm in diameter were demonstrated using SSD VB [32]. However, mild stenoses, submucosal infiltration, and superficial spreading tumours are not identified [32,33].…”

“…virtual bronchoscopy (VB)) produce remarkably high-quality and accurate reproductions of major endoluminal abnormalities ( fig. 2) [19,32,33]. VB has some advantages over real bronchoscopy: it is noninvasive, recurrent views can be created, and directions of view of the virtual endoscope may be changed interactively.…”

“…bronchogenic carcinoma, benign tumour, mucus plugging, blood clot, or foreign body) [33,35]. Many series have shown the excellent correlation between VB images and FOB results regarding the location, severity, and shape of airway narrowing [19,32,36]. VB is able to pass severe airway stenoses or obstructions, which is not possible using FOB.…”

Virtual endoscopic environments in modern neurosurgical practice

“…[37] In one study endoluminal space-occupying lesions of greater than 5 mm and stenosis of greater than 50% were detected quickly by virtual endoscopy in all cases. In addition, altered configurations based on external compression were always correctly identified.…”

“…It has been concluded that the upper limit for collimation is either 5 mm with a pitch of 1 or 3 mm with an increased pitch of 2 mm. [37] For practicality, it was determined that a collimation of 3 mm with a pitch of 1.5 mm and an overlapping reconstruction with an increment of 1 mm is optimum. These parameters maximize the data for producing 3-D reconstruction while minimizing the amount of radiation used in obtaining the study.…”