Clinical Utility of CT Imaging Techniques for Tracheobronchial Diseases cent major vessels or soft tissue mass, as well as providing a lymph node map. Using special software, Boisell et al. produced high-quality volume-rendering 3-D images of air- ways and lymph nodes against a background of spiral CT data (11). A study by Higgins et al. also included modified SSD images showing the complex geometry of the major airways, aorta, and a tumor (12). TCT preserves CT atten- uation and has high spatial resolution, and in our study it therefore provided the best information for the evaluation of the relationship between abnormalities and adjacent structures. MPR may occasionally provide additional infor- mation in some regions such as the aortopulmonary win- dow, and because it can render all image data, is superior in displaying both adjacent structures of the airway and pe- ripheral structures. In this study it was, however, less infor- mative than TCT and RCT, and was also relatively poor in evaluating the relationship between bilateral main bronchial lesions and adjacent structures. The main reason for this may be its lower longitudinal resolution. MPR, and particularly SSD, images can help provide a global understanding of tracheobronchial status, and we speculated that this is why both imaging techniques showed good grades for overall information. Such images are very useful in the diagnosis of congenital airway abnor- malities. SSD images usually depict the inner border of an airway instead of the true wall of the tracheobronchial tree, and their characterization of tracheobronchial lesions is therefore relatively poor; they merely demonstrate pat- terns of airway narrowing. Because it has better spatial res- olution than RCT, TCT was the most informative modality, and its characterization of bilateral main bronchial lesions, was superior to MPR. In conclusion, SSD and MPR were superior for the detec- tion, localization, and evaluation of the extent of airway disease, such images were especially useful in the prepara- tion of endobronchial procedures and in surgical planning. RCT alone cannot adequately evaluate tracheobronchial disease, and in the detection, localization, and determina- tion of the extent of lesions, the evaluation of their rela- tionship with adjacent structures, and characterization of airway disease, was less accurate than TCT. For the evalu- ation of suspected or known endobronchial abnormality, 3-D CT based on TCT is therefore the method of choice. References 1. Quint LE, Whyte RI, Kazerooni EA, et al. Stenosis of the central airways: evaluation by using helical CT with multiplanar recon- struction. Radiology 1995;194:871-877 2. Sagy M, Poustchi-Amin M, Nimkoff L, Silver P, Shikowitz M, Leonidas JC. Spiral computed tomographic scanning of the chest with three dimensional imaging in the diagnosis and manage- ment of paediatric intrathoracic airway obstruction. Thorax 1996;51:1005-1009 3. LoCicero J, Costello P, Campos CT, et al. Spiral CT with multi- planar and three-dimensional reconstructions accurately predicts tracheobronchial pathology. Ann Thorac Surg 1996;62;811-817 4. Kauczor HU, Wolcke B, Fischer B, Mildenberger P, Lorenz J, Thelen M. Three-dimensional helical CT of the tracheobronchial tree: evaluation of imaging protocols and assessment of suspected stenoses with bronchoscopic correlation. AJR 1996;167:419-424 5. Lacrosse M, Trigaux JP, Van Beers BE, Weynants P. 3D spiral CT of the tracheobronchial tree. J Comput Assist Tomogr 1995; 19:341-347 6. Gurney JW. Missed lung cancer at CT: imaging findings in nine patients. Radiology 1996;199:117-122 7. Whyte RI, Quint LE, Kazerooni EA, Cascade PN, Iannettoni MD, Orringer MB. Helical computed tomography for the evalu- ation of tracheal stenosis. Ann Thorac Surg 1995;60;27-31 8. Hernandez RJ, Tucker GF. Congenital tracheal stenoses: role of CT and high kV films. Pediatr Radiol 1987;17:192-196 9. Lee KS, Yoon JH, Kim TK, Kim JS, Chung MP, Kwon OJ. Evaluation of tracheobronchial disease with helical CT with multiplanar and three-dimensional reconstruction: correlation with bronchoscopy. RadioGraphics 1997;17:555-567 10. Naidich DP, Gruden JF, McGuinness G, McCauley DI, Bhalla M. Volumetric (helical/spiral) CT (VCT) of the airways. J Thorac Imag 1998;12:11-28 11. Boiselle PM, Patz EF Jr, Vining DJ, Weissleder R, Shepard JA, McLoud TC. Imaging of mediastinal lymph nodes: CT, MR, and FDG PET. RadioGraphics 1998;18:1061-1069 12. Higgins WE, Ramaswamy K, Swift RD, McLennan G, Hoffman EA. Virtual bronchoscopy for three-dimensional pulmonary im- age assessment: state of the art and future needs. RadioGraphics 1998;18:761-778 Korean J Radiol 1(3), September 2000 141