Diagnostic Effectiveness of Virtual Bronchoscopy

This study will evaluate a new technique for examining the air passages of the lungs called "virtual bronchoscopy." It involves using computed tomography (CT) images of the chest to generate a 3-dimensional model of the walls of the trachea and bronchi (airway passages). This non-invasive method lets doctors see small masses and areas of narrowing in the passages without having to do surgery or pass a tube through them. Patients with diseases of the air passages who are enrolled in an NIH clinical trial may participate in this study, which requires having a CT scan. The patient lies on a table that slowly slides into a hole in a donut-shaped X-ray machine (the scanner). Patients may have to hold their breath several times during the procedure. Some patients may be given an injection of a contrast agent through a catheter (thin tube) placed in an arm vein to improve visibility of abnormalities. Patients may also be asked to breathe oxygen through nasal prongs to allow them to hold their breath longer. The procedure usually takes 15 to 20 minutes.

This project is a test of the efficacy of a new diagnostic method for imaging the airways known as virtual bronchoscopy. Virtual bronchoscopy is performed by acquiring thin section computed tomography (CT) images of the chest. These images are used to generate a three dimensional model of the tracheal and bronchial walls on a graphics workstation in 3-D. The model can be manipulated to allow the viewer to "fly through" the tracheobronchial tree providing views similar to those obtained during bronchoscopy. The technique produces a display of the human bronchial system in a readily understood format. Moreover, it allows investigation of post-stenotic portions of the bronchial tree that are beyond the reach of fiberoptic bronchoscopy. Further, virtual bronchoscopy may be used to guide interventional procedures. The patients that will be studied in this protocol will be those having inflammatory, infectious, or neoplastic pulmonary processes who would have had a chest CT for clinical reasons. These patients will be recruited from current NIH protocols. The study design consists of scanning of the thorax using thin section helical CT, followed by three dimensional surface rendering of the airways and transfer of the digital data to videotape. In one of four parts of the protocol, the virtual bronchoscopy will be compared with results from fiberoptic bronchoscopy in a blinded study. In a second part of the protocol, the virtual bronchoscopy will be used to perform a descriptive analysis of cavitary lung lesions. In the third part, the utility of virtual bronchoscopy in diagnosis of neoplastic lesions of the chest will be studied. In the fourth part, certain technical problems in the virtual bronchoscopy procedure will be investigated. The patients will only have fiberoptic bronchoscopy for clinically indicated purposes. We anticipate that virtual bronchoscopy will be diagnostically efficacious for disorders which produce a morphologic alteration in bronchial anatomy.