Spiral CT evaluation of the trachea and bronchi

Preoperative evaluation of stage T3, central-type non-small cell lung cancer with double sleeve lobectomy under complete video-assisted thoracoscopic surgery using spiral computed tomography post-processing techniques

BACKGROUND

To investigate the estimated value of spiral computed tomography (CT) post-processing techniques in preoperative stage T3, central-type non-small cell lung cancer (NSCLC) with double sleeve lobectomy under complete video-assisted thoracoscopic surgery (c-VATS).

METHODS

Preoperative clinical date and CT reconstructed data of 10 patients who underwent double sleeve lobectomy with upper lobe stage T3, central-type NSCLC were retrospectively analysed and compared to surgical pathological results and cross-sectional CT data. The diagnostic criterions of tumour invasion of pulmonary artery and bronchus were divided into five grades, which included estimation of upper lobe pulmonary arteries and bronchi (40 branches, respectively).

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of cross-sectional CT images of pulmonary artery tumour invasion were 78.57%, 58.33%, 81.48%, 53.85%, and 72.50%, respectively, while the respective values for CT reconstructed images were 93.55%, 87.50%, 96.67%, 70.00%, and 90.00%, showing statistical significance (χ(2)=4.021, P=0.045). Similarly, the evaluate, the sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of cross-sectional CT images of bronchial tumour invasion were 82.76%, 45.45%, 80.00%, 50.00%, and 72.50%, respectively, while the respective values for CT reconstructed images were 97.06%, 66.67%, 94.29%, 80.00%, 92.50%; these results were also statistically significant (χ(2)=5.541, P=0.019).

CONCLUSIONS

The sensitivity, specificity, and diagnostic accuracy of the spiral CT post-processing techniques were better than cross-sectional CT images in estimating the extent of tumour invasion in the pulmonary arteries and bronchi of central-type NSCLC. CT post-processing techniques are essential tools in preoperative examination and operative method selection of central-type lung cancer with double sleeve lobectomy under c-VATS.

CT assessment of tracheobronchial anomaly in left pulmonary artery sling

BACKGROUND

The left pulmonary artery sling (LPAS) is a rare vascular anomaly where the left pulmonary artery arises from the right pulmonary artery, passes over the right bronchus, and goes posteriorly between the trachea and esophagus. The LPAS is frequently associated with cardiac and non-cardiac defects including tracheobronchial abnormalities.

OBJECTIVE

To evaluate the utility of multislice CT (MSCT) and helical CT (HCT) in diagnosing and defining the tracheobronchial anomaly and anatomic relationships between the trachea and aberrant left pulmonary artery.

MATERIALS AND METHODS

MSCT or HCT was performed in 27 children to determine the tracheobronchial anatomy and identify tracheobronchial stenosis. Eighteen children underwent surgery.

RESULTS

According to the Wells classification of LPAS, which includes two main types and two subtypes, there were eight cases of type 1A, five cases of type 1B, six cases of type 2A and eight cases of type 2B in this group. Twenty-four of the 27 children had substantial tracheobronchial stenosis. Four died before surgery; the 18 had reanastomosis of the left pulmonary artery. Five children also had tracheoplasty; three died after surgery.

CONCLUSION

CT, especially MSCT, is an ideal modality for simultaneously identifying aberrant left pulmonary artery and any associated tracheobronchial anomaly. The Wells classification is useful for operative planning.

MDCT of the airways: technique and normal results

The new generation of multidetector CT (MDCT) has revolutionized noninvasive imaging of proximal and distal airways. Exquisite anatomic details of the airway lumen and airway wall on axial CT images benefit in routine practice from postprocessing tools in adequate orientation. This method ensures an excellent assessment of the morphology and location of any pathology. It may be combined with use of very low dose CT. Airway lumen and airway wall areas may be quantitatively assessed on MDCT images by using specific techniques that are reproducible and accurate.

Role of spiral computed tomography with 3-dimensional reconstruction in cases with laryngeal stenosis--a radioclinical correlation

PURPOSE

To study the efficacy of spiral computed tomography with 3-dimensional reconstruction (SCT-3DI) and endoscopy in cases with laryngeal stenosis with regard to site, type, grade, and length of stenosis and to determine the correlation among the findings of SCT-3DI, endoscopy, and surgery.

MATERIAL AND METHODS

This prospective study on 30 cases of laryngotracheal stenosis (acquired = 28 cases, congenital = 2 cases) was conducted in the Department of Otorhinolaryngology and Head Neck Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India, from 2001 to 2003. All patients were evaluated by SCT-3DI and rigid endoscopy. Twenty-three patients underwent open surgical procedure, and 7 patients underwent endoscopic dilatation. Correlation was established among the findings of SCT-3DI, endoscopy, and surgery by Pearson correlation coefficient (r), paired t test, and chi(2) test.

RESULTS

Findings of SCT-3DI, endoscopy, and surgery were found to well correlate with each other. SCT-3DI was found to be less accurate in measuring the exact length of stenosis but could measure the length of stenosis in all cases, whereas by endoscopy, the measurements could be made accurately in 14 cases (46.6%). The endoscopy was more accurate in diagnosing the site and grade of stenosis (P < .01). SCT-3DI gave 18.6% false-positive result regarding involvement of glottis in stenosis. A significant difference was found between endoscopy and SCT-3DI for grade III and IV stenoses (P < .01), and SCT-3DI found to give false-positive result in 19.2% cases for grade IV stenosis. SCT-3DI was found to be a better diagnosing modality in differentiating the circumferential Gupta and Parida. SCT-3DI was found to give a false-positive result in 19.2% cases for grade IV stenosis. SCT-3DI was found to be better a diagnosing modality in differentiating the circumferential and eccentric stenosis (P < .01) and to detect the cricoid and thyroid cartilage fracture, double stenosis, and laryngocele. A false-positive rate of 33.3% was seen in diagnosing fracture of cricoid cartilage on radiology.

CONCLUSION

The findings of SCT-3DI, endoscopy, and surgery well correlated with each other. Findings of SCT-3DI and rigid endoscopy are complementary to each other for a better surgical planning and outcome.

Multimodal virtual bronchoscopy using PET/CT images

OBJECTIVE

To demonstrate the possibilities, advantages and limitations of virtual bronchoscopy using data sets from positron emission tomography (PET) and computed tomography (CT).

MATERIALS AND METHODS

Eight consecutive patients with non-small cell lung cancer (NSCLC) underwent PET/CT. PET was performed with a glucose analog, 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG), using a state-of-the-art full-ring Pico-3D PET scanner. CT was performed with a venous-dominant contrast-enhanced phase using a 16-slice CT scanner. The tracheobronchial system was segmented using the CT data set with an interactive threshold interval volume-growing segmentation algorithm. The primary tumors and lymph node metastases were segmented for virtual CT-bronchoscopy using the CT data set and for virtual hybrid bronchoscopy using the PET/CT data set. The structures of interest were visualized with a color-coded shaded-surface rendering method.

RESULTS

The use of CT and virtual CT-bronchoscopy primarily facilitates visualization of the anatomical details of the tracheobronchial system and detection of anatomical/morphologic structural changes caused by disease. PET/CT and virtual hybrid bronchoscopy, or virtual PET/CT-bronchoscopy, give superior results to virtual CT-bronchoscopy because the hybrid bronchoscopy uses both the CT information and the molecular/metabolic information about the disease obtained from PET.

CONCLUSIONS

PET/CT imaging has proven to be a highly valuable oncological diagnostic modality. Virtual hybrid bronchoscopy can be performed using a low-dose CT scan or diagnostic CT. However, it is expected to improve diagnostic accuracy in identification and characterization of malignancies, verification of infections, and differentiation of viable tumor tissue from atelectases and scar tissue, as well as assessment of tumor staging and therapeutic response, and detection of early stage recurrences that are not detectable or are liable to be misjudged using virtual CT-bronchoscopy. It could also be useful as a screening examination method for patients with suspected endobronchial malignancy. Virtual hybrid bronchoscopy with a transparent color-coded shaded-surface rendering model offers a useful alternative to fiberoptic bronchoscopy, and is particularly promising for patients for whom fiberoptic bronchoscopy is not feasible, contraindicated or refused.

Evaluation of obstructive airway lesions in complex congenital heart disease using composite volume-rendered images from multislice CT

BACKGROUND

Multislice CT (MSCT) allows high-quality volume-rendered (VR) and composite volume-rendered images.

OBJECTIVE

To investigate the clinical usefulness of composite VR images in the evaluation of the relationship between cardiovascular structures and the airway in children with complex congenital heart disease (CHD).

MATERIALS AND METHODS

Four- or 16-slice MSCT scanning was performed consecutively in 77 children (mean age 6.4 months) with CHD and respiratory symptoms, a chest radiographic abnormality, or abnormal course of the pulmonary artery on ECHO. MSCT scanning was performed during breathing or after sedation. Contrast medium (2 ml/kg) was administered through a pedal venous route or arm vein in all patients. The VR technique was used to reconstruct the cardiovascular structures and airway, and then both VR images were composed using the commercial software (VoxelPlus(2); Daejeon, Korea).

RESULTS

Stenoses were seen in the trachea in 1 patient and in the bronchi in 14 patients (19%). Other patients with complex CHD did not have significant airway stenoses.

CONCLUSIONS

Composite VR images with MSCT can provide more exact airway images in relationship to the surrounding cardiovascular structures and thus help in optimizing management strategies in treating CHD.

Effects of ECG Gating and Postprocessing Techniques on 3D MDCT of the Bronchial Tree

OBJECTIVE

Our goal was to determine the impact of ECG gating and different postprocessing techniques on 3D imaging of the bronchial tree. SUBJECTS AND METHODS. Retrospective ECG-gated MDCT and non-ECG-gated MDCT of the chest were performed in 25 patients. ECG-gated MDCT data were reconstructed mid diastole using a fixed interval of -400 msec in 25 patients and then additionally at -200, -300, and -500 msec in 10 of those patients. Shaded surface display and volume rendering of the bronchial tree combined with virtual bronchoscopy were performed using all data sets. The extent of bronchial tree visualization in shaded surface display-virtual bronchoscopy and volume rendering-virtual bronchoscopy and the presence of artifacts in volume-rendered images were scored by three blinded reviewers. The effective radiation doses of the ECG-gated and nongated acquisitions were compared.

RESULTS

The summary scores of all bronchial segments for gated shaded surface display-virtual bronchoscopy and gated volume rendering-virtual bronchoscopy did not differ significantly. The summary scores for nongated shaded surface display-virtual bronchoscopy and nongated volume rendering-virtual bronchoscopy were not significantly different. Non-gated acquisition yielded significantly better visualization of the bronchial tree for both post-processing techniques, regardless of the time interval used for reconstruction of the ECG-gated series. Artifact scores in volume-rendered images were significantly higher for ECG-gated MDCT compared with nongated MDCT. Effective radiation dose was significantly higher for the ECG-gated acquisition.

CONCLUSION

Given the advantage of volume rendering for representing the entire data set and given the lower radiation dose and better 3D image quality of nongated acquisition, volume rendering performed on nongated MDCT data is the method of choice for 3D visualization of the bronchial tree.

Virtual bronchoscopy: comparison of different surface rendering models

The aim of this study was to compare different representation models of surface-rendered virtual bronchoscopy. 10 consecutive patients with inoperable primary lung tumors underwent thin-section spiral computed tomography. The structures of interest, the tracheobronchial system and anatomical and pathological thoracic structures were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with the aid of a color-coded surface rendering method. For virtual bronchoscopy, the tracheobronchial system was visualized using a triangle-surface rendering model, a shaded-surface rendering model and a transparent shaded-surface rendering model. The triangle-surface rendering model allowed optimum detailed spatial representation of the dimensions of extraluminal anatomical and pathological mediastinal structures. As the lumen of the tracheobronchial system was less well defined, the rendering model was of limited use for depiction of the airway surface. The shaded-surface rendering model facilitated an optimum assessment of the airway surface, but the mediastinal structures could not be depicted. The transparent shaded-surface rendering model provides simultaneous adequate to optimum visualization and assessment of the intraluminal airway surface and the extraluminal mediastinal structures as well as a quantitative assessment of the spatial relationship between these structures. Fast data acquisition with a multi-slice detector spiral computed tomography scanner and the use of virtual bronchoscopy with the transparent shaded-surface rendering model obviate the need for time consuming detailed analysis and presentation of axial source images by providing improved the diagnostic imaging of endotracheal and endobronchial diseases and offering a useful alternative to fiberoptic bronchoscopy.

Hybrid 3D visualization of the chest and virtual endoscopy of the tracheobronchial system: possibilities and limitations of clinical application

OBJECTIVE

A hybrid rendering method which combines a color-coded surface rendering method and a volume rendering method is described, which enables virtual endoscopic examinations using different representation models.

MATERIALS AND METHODS

14 patients with malignancies of the lung and mediastinum (n=11) and lung transplantation (n=3) underwent thin-section spiral computed tomography. The tracheobronchial system and anatomical and pathological features of the chest were segmented using an interactive threshold interval volume-growing segmentation algorithm and visualized with a color-coded surface rendering method. The structures of interest were then superimposed on a volume rendering of the other thoracic structures. For the virtual endoscopy of the tracheobronchial system, a shaded-surface model without color coding, a transparent color-coded shaded-surface model and a triangle-surface model were tested and compared.

RESULTS

The hybrid rendering technique exploit the advantages of both rendering methods, provides an excellent overview of the tracheobronchial system and allows a clear depiction of the complex spatial relationships of anatomical and pathological features. Virtual bronchoscopy with a transparent color-coded shaded-surface model allows both a simultaneous visualization of an airway, an airway lesion and mediastinal structures and a quantitative assessment of the spatial relationship between these structures, thus improving confidence in the diagnosis of endotracheal and endobronchial diseases.

CONCLUSIONS

Hybrid rendering and virtual endoscopy obviate the need for time consuming detailed analysis and presentation of axial source images. Virtual bronchoscopy with a transparent color-coded shaded-surface model offers a practical alternative to fiberoptic bronchoscopy and is particularly promising for patients in whom fiberoptic bronchoscopy is not feasible, contraindicated or refused. Furthermore, it can be used as a complementary procedure to fiberoptic bronchoscopy in evaluating airway stenosis and guiding bronchoscopic biopsy, surgical intervention and palliative therapy and is likely to be increasingly accepted as a screening method for people with suspected endobronchial malignancy and as control examination in the aftercare of patients with malignant diseases.

Spiral CT optimization for measurement of bronchial lumen diameter using an experimental model

The aim of the study was to determine optimal parameters for demonstrating sublobar bronchi on spiral CT. Measurements were obtained from five parallel polyethylene tubes embedded in foam matrix with similar radiographic characteristics to segmental and subsegmental bronchi and to lung parenchyma, respectively. Collimation widths of 1.5, 2, 3 and 4 mm were used, with a pitch of 1 or 1.5 and a reconstruction interval of 1 mm or 2 mm. Various slice planes were used. Images acquired orthogonally were viewed normally. Images acquired in planes oblique or parallel to the long axes of the tubes were reformatted into a plane orthogonal to the long axes of the tubes to be comparable with the directly acquired orthogonal images. Tube diameters were measured at lung window settings (L, -400; W, 1300) and compared with known true inner and outer tube diameters. Measurements from images acquired orthogonal to the tube long axes were accurate regardless of slice thickness. Images acquired obliquely or parallel only produced accurate measurements at the lowest slice thickness (1.5 mm). Pitch and reconstruction interval had no effect on measurement error in any scan plane. It is concluded that a slice thickness of 1.5 mm or less, with a pitch of 1.5, should be used when acquiring images at angles other than orthogonal to the long axes of experimental tubes equivalent to the segmental and subsegmental bronchi. It is suggested that similar parameters should be used in vivo and that the examination should be targeted to the area of the bronchial tree in question to reduce patient dose and length of breath-hold.

Evaluation of airway obstruction using virtual endoscopy

OBJECTIVES

This study examines the use of virtual endoscopy (VE) in the evaluation of patients with upper airway obstruction. The utility of VE compared with actual endoscopy was investigated with respect to accuracy of diagnosis and reproduction of endoscopic images.

STUDY DESIGN

A random cohort of 30 patients with various causes of airway obstruction was examined.

METHODS

The computed tomography (CT) data were reconstructed using a proprietary VE software program, FreeFlight, blind to the actual endoscopic findings. The cause of obstruction was identified and compared with actual endoscopic findings. This included 21 patients with airway stenoses, 8 patients with laryngotracheomalacia, 3 tracheal tumors, 2 glottic webs, 5 patients with innominate artery compression, 2 tracheal granulomas, and 7 patients with impaired true vocal cord mobility.

RESULTS

Virtual endoscopic evaluation was accurate in assessing stenosis width and length of fixed airway lesions. Correlation of stenosis shape and contour between actual endoscopy and VE was excellent. The stenosis-to-lumen ratios were compared between VE and actual endoscopy and were found to be within 10% (SD = 8). However, virtual endoscopic evaluation could not illustrate one of the glottic webs, half of the cases of tracheomalacia, or any of the cases of impaired true vocal cord mobility.

CONCLUSIONS

Virtual endoscopy was not as sensitive as actual endoscopy in detecting the cause of airway obstruction that was based on dynamic movement. However, VE was excellent for the measurement and definition of fixed airway lesions.

Diagnostic potential of virtual bronchoscopy: advantages in comparison with axial CT slices, MPR and mIP?

The aim of this study was to evaluate the diagnostic potential of virtual endoscopy (VE) and to compare it with axial CT slices, multiplanar reconstructions (MPR), minimal intensity projections (mIP), and bronchoscopy in patients diagnosed with bronchogenic carcinoma. Thirty patients underwent a spiral CT. Axial CT images were transferred to an Onyx workstation (Silicon Graphics, Sun Microsystems, Mountain View, Calif.) for performing virtual endoscopy. Accuracy for this procedure was tested by three radiologists on a monitor in comparison with axial CT slices, MPR, mIP, and bronchoscopy concerning the localization and degree of stenoses. Endoluminal tumors were identified by virtual bronchoscopy with no statistically significant difference of localization or grading of stenosis in comparison with bronchoscopy, axial CT slices, MPR and mIP. Axial CT slices, MPR, and mIP showed poorer results with over- or underestimation of stenoses compared with VE and bronchoscopy. Passing of stenoses was only possible with VE in 5 patients. Virtual endoscopy is a non-invasive method for identification of endoluminal tumors and is comparable to real bronchoscopy.

Virtual bronchoscopy

Three-dimensional endoluminal tracheobronchial simulations can be derived successfully from thoracic helical CT scans, and can reproduce the appearances of major endobronchial abnormalities confirmed during FB. The prospects of ever-faster CT scanners (capable of submillimeter resolution) merged with greater computer power make it likely that current versions of virtual bronchoscopy images will seem primitive in the future. Initial descriptive reports suggest great potential, but the startling visual appeal of these 3-D portrayals of a patient's airway and mediastinal anatomy and the prospects of exploring this information in real time do not establish its clinical role. Such virtual bronchoscopy findings are generally predictable on the basis of currently available axial CT images alone. The extent to which these 3-D endobronchial renderings improve the already high predictive values of CT requires critical study. In their patients with lung cancer Cicero et al observed that neither the staging nor diagnosis was modified substantially, but virtual bronchoscopy contributed to enhanced understanding of the pathology of the neoplastic process. Whether this added perspective translates to tangible benefits for patients is an intriguing possibility that has yet to be proved. The unique 3-D endobronchial view may offer particular advantages in some individuals and contribute to the patient's noninvasive evaluation. Because of the already high yield of conventional CT, diagnostic yield alone is not likely to be the sole best measure of this evolving technology. Accordingly, future multidisciplinary research investigations will also need to prospectively address nuances of decision-making and measure appropriate patient outcomes. In these efforts the active dialogue between chest clinician and radiologist will remain essential to defining and realizing the true potential of virtual bronchoscopy.

Tracheal involvement in Wegener's granulomatosis: evaluation using spiral CT

OBJECTIVE

To describe the computed tomography (CT) appearances of tracheal stenosis in Wegener's granulomatosis (WG) and to assess the additional value of reformatted images.

PATIENTS AND METHODS

Ten patients with tracheal involvement by WG were assessed with spiral CT and both coronal and three-dimensional surface shaded images were generated. Fibreoptic bronchoscopy was also performed in all patients.

RESULTS

Ninety per cent of lesions were situated in the subglottic region. In all cases there was circumferential mucosal thickening, in nine cases extending over a relatively short distance (mean 2.4 cm). The degree of narrowing of the axial luminal diameter ranged from 23% to 100%. In three patients there was contiguous involvement of the vocal cords evident on CT, two further cases with mild vocal cord inflammation were identified bronchoscopically. Other CT findings included mucosal irregularity and ulceration (50%), and involvement of the tracheal cartilages (20%).

CONCLUSION

Wegener's granulomatosis may involve the trachea with resultant stenosis. Spiral CT is an easily performed, non-invasive technique which provides accurate assessment of tracheal lesions and is complementary to bronchoscopy. The main additional advantage of coronal reformatted images was our added confidence in defining the upper and lower limits of lesions and in the evaluation of vocal cord involvement.

Thin-section spiral volumetric CT for the assessment of lobar and segmental bronchial stenoses

Thin-section volumetric computed tomography (CT) was used to examine the lobar and segmental bronchi of five patients who had stenoses of these airways diagnosed by previous bronchography and/or bronchoscopy. Four of 23 lobar bronchi and 42 of 72 segmental bronchi were judged to be stenotic by CT. Our findings in this small group suggest that thin-section volumetric CT is a promising non-invasive technique that is likely to prove useful in the assessment of such stenoses in the future.

Three-dimensional endoscopic mode for observation of laryngeal structures by helical computed tomography

We produced high-quality three-dimensional (3D) endoscopic images of the larynx using helical scanning computed tomography. Subjects included two normal volunteers and 10 patients: five with laryngeal cancer, four with unilateral recurrent laryngeal nerve (RLN) palsy, and one with atrophied vocal folds. Two vertically split hemilaryngeal images were displayed together with the oral and tracheal views. Although motion artifacts were seen in four patients, laryngeal structures including the vocal fold, ventricular fold, and ventricle were clearly identified in all subjects. In the patients with cancer, axial images showing the extent of the tumor in each patient provided more information than 3D endoscopic images. In the patients with RLN palsy and atrophied vocal fold, combination of 3D endoscopic and cross-sectional images offered more diagnostic information than axial images alone.

Three-dimensional imaging of the pediatric airway

Accurate imaging of the pediatric tracheobronchial tree is indicated for the evaluation of congenital or acquired abnormalities. Conventional axial computed tomography (CT) is now considered the best imaging modality for evaluation of the trachea and major bronchi, and has almost completely replaced the former gold standard of tracheobronchography. Preliminary results indicate that CT scan performance is further enhanced through the application of spiral technology and two-dimensional (2D) and 3D representation of the tracheobronchial tree. Spiral CT scans with 3D surface rendering offers an opportunity to replace traditional tracheobronchography with a safer, less invasive modality.

Spiral computed tomography with 3-dimensional reconstruction for the diagnosis of tracheobronchial stenosis

We report on the usefulness of spiral computed tomography (CT) with 3-dimensional (3D) reconstruction in the diagnosis of tracheobronchial abnormalities based on three cases of children with congenital tracheobronchial strictures. Images were reconstructed using a curved planar reformat and shaded surface display. The images obtained from our three cases of tracheal stenosis, subglottic stenosis and tracheobronchial strictures were extremely clear. Spiral CT with 3D reconstruction provides excellent anatomic delineation of the tracheobronchial airway, and is safe and less invasive than tracheobronchography.

Spiral computed tomographic scanning of the chest with three dimensional imaging in the diagnosis and management of paediatric intrathoracic airway obstruction

BACKGROUND

The usefulness of spiral computed tomographic (CT) scans of the chest with three dimensional imaging (3D-CT) of intrathoracic structures in the diagnosis and management of paediatric intrathoracic airway obstruction was assessed.

METHODS

A retrospective review was made of five consecutive cases (age range six months to four years) admitted to the paediatric intensive care unit and paediatric radiology division of a tertiary care children's hospital with severe respiratory decompensation suspected of being caused by intrathoracic large airway obstruction. Under adequate sedation, the patients underwent high speed spiral CT scanning of the thorax. Non-ionic contrast solution was injected in two patients to demonstrate the anatomical relationship between the airway and the intrathoracic large vessels. Using computer software, three-dimensional images of intrathoracic structures were then reconstructed by the radiologist.

RESULTS

In all five patients the imaging results were useful in directing the physician to the correct diagnosis and appropriate management. In one patient, who had undergone repair of tetralogy of Fallot with absent pulmonary valve, the 3D-CT image showed bilateral disruptions in the integrity of the tracheobronchial tree due to compression by a dilated pulmonary artery. This patient underwent pulmonary artery aneurysmorrhaphy and required continued home mechanical ventilation via tracheostomy. In three other patients with symptoms of lower airway obstruction the 3D-CT images showed significant stenosis in segments of the tracheobronchial tree in two of them, and subsequent bronchoscopy established a diagnosis of segmental bronchomalacia. These two patients required mechanical ventilation and distending pressure to relieve their bronchospasm. In another patient who had undergone surgical repair of intrathoracic tracheal stenosis three years prior to admission the 3D-CT scan ruled out restenosis as the reason for her acute respiratory decompensation.

CONCLUSIONS

3D-CT scanning is a useful additional diagnostic tool for intrathoracic airway obstruction in paediatric patients.

Tracheobronchial tree: three-dimensional spiral CT with bronchoscopic perspective

The purpose of this report is to describe an original 3D technique that permits bronchoscopic perspective simulations of the tracheobronchial tree on an affordable workstation. Software based on surface shading was developed to permit navigation through the central airways using spiral CT data. Multiplanar reformations are displayed simultaneously with the virtual bronchoscopy simulations to give information about tissues surrounding the airways. Two clinical examples are reported to illustrate the value of this advanced computer technique.

Virtual tracheo-bronchial endoscopy: educational and diagnostic value

The use of Helical CT significantly improves image quality of examinations in a number of clinical settings. It is particularly suited to the study of the tracheo-bronchial tree as a result of new ways of image processing (developed by GEMS research) which can produce virtual endoscopic images without the use of an endoscope. We present our initial anatamo-radiological findings and their educational value as well as our thoughts on potential future clinical applications.