Neoplasms involving the respiratory system cause significant morbidity and mortality. Primary lung cancers account for approximately 160,000 deaths annually in the United States. In addition, nearly one third of all patients with neoplasms of nonpulmonary origin develop life-threatening pulmonary metastases. Frequently, patients with primary or metastatic cancers involving the respiratory tract have partial or complete bronchial obstructions secondary to endoluminal tumors or extrinsic compression. Noninvasive, reproducible, and objective methods for sequentially evaluating these abnormalities may prove useful for directing therapy and assessing the treatment response in these individuals, so
Patients with suspected tracheobronchial lesions typically undergo diagnostic evaluation consisting of conventional CT scanning and fiberoptic bronchoscopy (FB). Conventional two-dimensional crosssectional CT images of the chest have a reported sensitivity and specificity of 60 to 100% for the detection of obstructive lesions in the respiratory tract. The limitations of the accuracy of conventional CT scans include suboptimal scanning techniques, inappropriately thick slices, and artifacts between sections. Currently, FB remains the best modality for the evaluation of endoluminal and mucosal lesions in the respiratory tract. However, this imaging modality frequently provides little information concerning the extent of extraluminal disease or airway patency distal to high-grade bronchial stenoses.
Novel imaging modalities, such as super high-resolution CT (SHR-CT) scanning and virtual bronchoscopy (VB), are currently available for the non-invasive evaluation of tracheobronchial neoplasms. SHR-CT scanning involves the acquisition of several hundred images of the chest using a multislice helical CT scanner. Indeed, conventional CT scans may acquire only 20 to 50 images of the entire chest, High-resolution CT scans may image 50 contiguous cuts through a specific area of concern within the thorax. SHR-CT scans acquire 200 to 300 contiguous 1.25-mm cross-sections of the entire thorax. The radiation dose associated with SHR-CT scans is the same or slightly less than that of a conventional CT scan.