Virtual bronchoscopy in patients with central endobronchial stenosing lesions. Technique optimisation with single slice spiral CT.

PURPOSE: To describe an original protocol for single slice spiral Computed Tomography (CT) virtual bronchoscopy in the evaluation of patients with central airway stenoses and compare the results with fibreoptic bronchoscopy. MATERIALS AND METHODS: Ten patients (4 female and 6 male; age range 22-60 years; mean age 44 years) with endobronchial disease diagnosed by fibreoptic bronchoscopy (8 malignant tumours, 1 benign tumour and 1 fibroid stenosis) underwent virtual bronchoscopy with single slice spiral CT. A panoramic spiral CT scan of the whole chest was first obtained. Once the area of interest had been identified, a new contrast enhanced scan was performed, from bottom to top, with the following parameters: 2 mm slice thickness, 1 mm reconstruction index, 1.3 pitch, 120 Kvp, 80 mAs. Virtual bronchoscopy was generated with an upper threshold of -500 HU from the cross-sectional images of the second scan on a dedicated workstation. Axial, multiplanar reformations (MPR), and virtual endoscopy simulation were simultaneously visualised. Virtual CT bronchoscopy findings were compared with those of fibreoptic bronchoscopy. RESULTS: The protocol we used to perform single slice spiral CT virtual bronchoscopy enabled us to obtain virtual bronchoscopy images that correlated well with fibreoptic bronchoscopy findings in all cases, as well as allowing the visualization of the airways beyond the stenoses. Information about tissues surrounding the tracheobronchial tree was also available from axial and MPR images. Only in 1 case were motion artefacts observed. CONCLUSIONS: The set of the most appropriate parameters for performing virtual bronchoscopy by single slice spiral CT has not yet been standardized. In our opinion the appropriate selection of the protocol to adequately realize virtual bronchoscopic images is crucial when using CT devices such as the above, so as to achieve the correct balance between the quality of image definition and exposure dose