DOI: 10.1148/radiol.2422060153
(Radiology 2007;242:542-549.)
© RSNA, 2007
Tracheobronchial Anomalies and Stenoses: Detection with Low-Dose Multidetector CT with Virtual Tracheobronchoscopy—Comparison with Flexible Tracheobronchoscopy1
Christoph M. Heyer, MD,
Thomas G. Nuesslein, MD,
David Jung, MD,
Soeren A. Peters, MD,
Stefan P. Lemburg, MD,
Christian H. L. Rieger, MD and
Volkmar Nicolas, MD
1 From the Institute of Diagnostic Radiology, Interventional Radiology and Nuclear Medicine, BG Clinics Bergmannsheil, Ruhr-University of Bochum, Buerkle-de-la-Camp Platz 1, D-44789 Bochum, Germany (C.M.H., S.A.P., S.P.L., V.N.); and Children's University Hospital, St Josef Hospital, Ruhr-University of Bochum, Germany (T.G.N., D.J., C.H.L.R.). Received January 26, 2006; revision requested March 24; revision received April 3; accepted May 9; final version accepted June 8.
Address correspondence to C.M.H. (e-mail: christoph.heyer{at}rub.de).
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ABSTRACT
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Purpose: To prospectively assess the sensitivity and specificity of low-dose multidetector computed tomography (CT) with virtual tracheobronchoscopy (VT) for evaluation of suspected airway stenoses and/or abnormalities by using flexible tracheobronchoscopy (FT) as the reference standard.
Materials and Methods: The study was approved by the local ethics committee; parental consent was obtained. Forty-five patients with clinically and/or radiographically suspected tracheobronchial stenosis and/or anomaly underwent FT and contrast material–enhanced single-phase multidetector CT with VT. CT was performed with an age- and weight-adjusted low-dose protocol: 120 or 80 kV; 120 or 60 mA; collimation, 1.5 or 0.75 mm; gantry rotation, 0.5 second. Mean effective dose was calculated for all examinations. Postprocessing was performed with surface rendering of VT images and multiplanar reformations. CT images were analyzed in consensus by two radiologists who were blinded to FT results. Statistical analysis was performed with 2 x 2 contingency tables; 95% confidence intervals (CIs) were calculated with the Blyth-Still-Casella procedure.
Results: Mean patient age was 4.4 years (range, 2 months to 16 years; 53% male patients). Tracheobronchial narrowing and/or abnormality were depicted at FT in 38 of 45 patients. In 33 of 38 patients, multidetector CT with VT depicted a tracheobronchial narrowing and/or anomaly. In 10 of 38 patients, tracheobronchial stenosis was induced by vascular anomalies. Five patients with normal findings at multidetector CT with VT had tracheobronchomalacia with inspiratory airway stenosis at FT. Sensitivity and specificity of CT with VT were 86.8% (95% CI: 73.3%, 94.7%) and 85.7% (95% CI: 44.6%, 99.3%), respectively. Positive and negative predictive values were 97.1% (95% CI: 84.9%, 99.9%) and 54.5% (95% CI: 25.0%, 80.0%), respectively. Overall accuracy was 86.7% (95% CI: 74.3%, 94.0%). Mean effective dose was 1.1 mSv (range, 0.5–1.8 mSv).
Conclusion: Multidetector CT with VT with a low-dose protocol had high sensitivity and specificity for depiction of tracheobronchial narrowings and/or anomalies. However, tracheal narrowing due to tracheobronchomalacia was difficult to diagnose at single-phase multidetector CT with VT.
© RSNA, 2007
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INTRODUCTION
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With the acquisition of isotropic data sets, multidetector computed tomography (CT) can be used to generate thin-section virtual tracheobronchoscopic (VT) images with surface-rendering techniques. This application, which enables a three-dimensional, realistic, and detailed overview of the tracheobronchial system, has been used successfully in adult patients mainly to evaluate endobronchial tumor growth (1–6) and to perform follow-up examinations after interventions (7–9). To date, multidetector CT with VT has rarely been applied in children, and the primary focus was on detection of foreign bodies (10,11) and tracheobronchial anomalies (12,13). Although efforts have been made to define pediatric low-dose CT protocols (14–16), the primary reason for not routinely using CT with VT in children remains radiation exposure. Thus, the purpose of our study was to prospectively assess the sensitivity and specificity of low-dose multidetector CT with VT for the evaluation of suspected airway stenoses and/or abnormalities in patients by using flexible tracheobronchoscopy (FT) as the reference standard.
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MATERIALS AND METHODS
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No industry gave support specifically for this study. Furthermore, none of the authors is an employee or consultant for an industry whose products were evaluated in this study.
Patient Group
All patients who were admitted to the Children's University Hospital of the Ruhr-University of Bochum, Germany, between February 2004 and October 2005 and who underwent FT for possible tracheobronchial narrowing and/or anomaly were considered eligible to enter the study and underwent multidetector CT with VT. Indication for performing FT was on the basis of results on conventional chest radiographs that suggested a vascular anomaly, a history of persistent airway obstruction (abnormal breathing sounds, persisting or recurrent pulmonary infections), and/or abnormal findings at pulmonary function tests or physical examination (abnormal breathing sounds, stridor, dyspnea). Patients with a history of foreign-body aspiration, patients with known allergy to contrast material or with renal insufficiency, and those whose parents denied informed consent for FT and/or multidetector CT were excluded from the study group. The parents of each patient, after they were made aware of the radiation exposure at multidetector CT, gave written informed consent for the procedures and for the research protocol. The study was approved by the Ethics Committee of the Ruhr-University of Bochum, Germany.
A total of 49 patients suspected of having tracheobronchial stenoses and/or abnormalities were considered eligible to enter the study and to undergo FT and multidetector CT with VT. During the study interval, four patients were excluded because parents denied informed consent. Forty-five patients entered the study group.
Tracheobronchoscopic Procedure
All FTs were performed at the Children's Hospital of the Ruhr-University of Bochum, Germany, with standard fiberoptic bronchoscopes (BF-P40 or BF-N20; Olympus, Hamburg, Germany) through the nasal cavity by one of two senior bronchoscopists (T.G.N., C.H.L.R.; 12 and 25 years of bronchoscopic experience, respectively) with the use of sedation with pethidine (Dolantin; Aventis Pharma, Frankfurt, Germany) and midazolam (Dormicum; Hoffmann-LaRoche, Basel, Switzerland). Central airways were anesthetized with lidocaine solution (Xylocain 4%; Astra, Wedel, Germany). Patients were breathing spontaneously with the use of supplemental oxygen throughout the procedure. All patients underwent cardiorespiratory monitoring with a standard pulse oximeter and electrocardiography. Results of FT were recorded according to standard protocols, and airway abnormalities and/or narrowings were documented if present; a narrowing was considered substantial if the estimated airway diameter was narrowed to less than 80% of the original diameter. Every examination was recorded with a standard videotape.
Multidetector CT and Image Analysis
Multidetector CT was performed at the Institute of Diagnostic Radiology, Interventional Radiology, and Nuclear Medicine, BG Clinics Bergmannsheil, Ruhr-University of Bochum, Germany, with a 16-section scanner (Somatom Sensation 16; Siemens, Erlangen, Germany) within 48 hours after conventional FT. Patients were examined in the supine position with elevated arms. A nonenhanced frontal scout view of the chest and upper abdomen (80 kV, 39 mA) was obtained first at all examinations. In all patients, intravenous contrast agent (iopamidol, Solutrast 300; Byk Gulden, Konstanz, Germany) was administered manually by the attending radiologist (C.M.H., 6 years of experience in pediatric chest CT) via a peripheral vein at a rate of approximately 2–3 mL/sec. A dose of 1.5 mL per kilogram of body weight was injected. Delay time after contrast material administration was adjusted to patient age and weight (patients < 1 year or < 10 kg, 15 seconds; 1–5 years or 10–20 kg, 20 seconds; > 5 years or > 20 kg, 25 seconds). An automated tracking system was not used. If possible, the examination was performed with breath holding at suspended inspiration. In younger, noncooperative patients, quiet breathing was tolerated. None of the patients were sedated or anesthetized for the scan procedure. None of the patients were excluded from the study group because of motion.
The examination was started by the attending radiologist (C.M.H.) in the examination room by using a start pedal. Coverage at multidetector CT began at the thoracic inlet with inclusion of the supraaortic branches and extended inferiorly to the level of the diaphragm. Data acquisition was performed in the caudocranial direction. Acquisition time was roughly 3–6 seconds. A low-dose protocol with the following scan parameters was used: 80 kV (patient age < 5 years or weight < 20 kg) or 120 kV (patient age > 5 years or weight > 20 kg); 60 mA (patient age < 5 years or weight < 20 kg) or 120 mA (patient age > 5 years or weight > 20 kg); collimation, 0.75 mm (patient age < 1 year or weight < 10 kg) or 1.5 mm (patient age >1 year or weight >10 kg); gantry rotation, 0.5 second; and table feed per rotation, 27 mm. In borderline situations, the protocol with the lower scan parameters (80 kV, 60 mA, and collimation of 1.5 mm) was used. Nonenhanced images were not obtained. All CT examinations were performed without complications and resulted in diagnostic image quality.
After acquisition of the raw data set, transverse images with a section thickness of 5 mm and an increment of 4 mm were created and displayed with standard lung and soft-tissue window settings. Furthermore, transverse images with a section thickness of 2 mm and an increment of 1 mm (collimation, 1.5 mm) or a section thickness of 1 mm and an increment of 0.75 mm (collimation, 0.75 mm) and a smooth kernel (B30f) were calculated. On the basis of these images, postprocessing, which included multiplanar reformations with sagittal and coronal views and three-dimensional VT images, was performed by using surface rendering at a workstation (Leonardo; Siemens). The image display produced perspective color and gray-scale images with a matrix of 512 x 512. The virtual endoscope was placed in the proximal part of the trachea, and the whole tracheobronchial system was systematically evaluated by moving the tip of the endoscope distally to all subsegmental bronchi by using a fly-through mode. Image analysis of transverse images, sagittal and coronal multiplanar reformations, and VT images was performed at a four-quadrant monitor of the workstation in consensus by two experienced radiologists (C.M.H., V.N.; 7 and 17 years of experience in thoracic CT interpretation, respectively) who were blinded to clinical symptoms and FT findings. On average, it took 21 minutes per examination to perform VT in the study group. All tracheobronchial narrowings less than 80% of the original airway diameter and abnormalities (accessory bronchi, missing bronchi, bronchial hypoplasia, abnormal branching, and central bronchiectasis) were documented. Pulmonary infiltrates were documented, if present.
CT dose index (volume) and dose-length product were recorded, and effective dose was calculated for every patient by taking age- and sex-dependent conversion factors into account. All dose-related calculations were performed by using software (CT-Expo; G. Stamm and H.D. Nagel, Hannover, Germany) (17).
Additional Imaging
Additional imaging studies were not used as proof of truth but were reviewed to complete the clinical diagnostic work-up. All patients in the study underwent conventional thoracic radiography, at which a single posteroanterior chest radiograph was obtained prior to FT and multidetector CT with VT. In two patients, an additional lateral radiograph and a barium-enhanced esophagogram were obtained. In 19 patients, a color Doppler echocardiographic study was performed, which included complete examination of the heart and the mediastinal vessels. In two patients, a conventional angiographic study of the heart and the mediastinal arteries was performed. All additional imaging studies were interpreted by experienced independent readers who were not involved in our study and who were not aware of the results of FT and multidetector CT with VT.
Statistical Analysis
Qualitative results regarding the depiction of tracheobronchial narrowings and/or abnormalities with multidetector CT with VT were defined as true-positive, true-negative, false-positive, and false-negative findings. A true-positive finding was classified as narrowing and/or abnormality noted at both image modalities (FT and multidetector CT with VT), whereas a true-negative finding was defined as absence of stenoses and/or airway abnormalities at FT and multidetector CT with VT. A false-positive finding was defined as an airway section noted as abnormal at multidetector CT with VT but normal at FT. A false-negative finding was defined as an airway section noted as normal at multidetector CT with VT but abnormal at FT. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy were calculated with 2 x 2 contingency tables. All values from operative characteristics were subject to exact 95% confidence interval estimation according to the Blyth-Still-Casella procedure (StatExact, version 6.0; Cytel Software, Cambridge, Mass).
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RESULTS
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The mean age of the study group was 4.4 years (age range, 2 months to 16 years); 24 (53%) of 45 were male patients.
Multidetector CT with VT and FT Findings
In 38 (84%) of 45 patients, findings of a tracheobronchial narrowing and/or abnormality were present at FT, whereas seven patients had normal findings at FT. In 33 (87%) of 38 patients, multidetector CT with VT demonstrated the FT diagnosis of a tracheobronchial anomaly and/or narrowing (Fig 1).
Five patients with normal findings at multidetector CT with VT had findings of tracheobronchial narrowing due to tracheobronchomalacia at inspiration at FT. Eleven patients had normal tracheobronchial findings at multidetector CT with VT; six patients had normal findings at both multidetector CT with VT and FT. All patients with proved tracheobronchial anomalies without narrowing (n = 9) had correctly identified findings at multidetector CT with VT.
In three patients, an tracheoesophageal H-type fistula could be confirmed at multidetector CT with VT (Fig 2); of those, only two had an accessory ostium at FT. In the third patient, the tracheoesophageal fistula was depicted only with multidetector CT with VT and not with FT (false-positive finding).
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Figure 2a: CT images in a 4-year-old boy with chronic pulmonary infections. (a) VT image shows accessory ostium (arrow) in dorsolateral wall of distal trachea. (b) Transverse sections show presence of filiform tracheoesophageal H-type fistula (arrow).
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Figure 2b: CT images in a 4-year-old boy with chronic pulmonary infections. (a) VT image shows accessory ostium (arrow) in dorsolateral wall of distal trachea. (b) Transverse sections show presence of filiform tracheoesophageal H-type fistula (arrow).
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The presence of vascular abnormalities that cause tracheal narrowing was confirmed in 10 (26%) of 38 patients; a brachiocephalic trunk was the most common finding (eight patients) (Figs 3, 4). In nine of 10 patients with vascular anomalies, the bronchoscopist had noted pulsatile compression of the trachea. In two patients, a double aortic arch with vascular ring formation and subsequent tracheal stenosis was diagnosed at multidetector CT with VT (Fig 5) and confirmed at conventional angiography. In a 3-year-old patient, an aberrant right subclavian artery was found, but tracheal narrowing, which was diagnosed as being caused by tracheomalacia at FT, could not be confirmed at multidetector CT with VT. In two patients, tracheal narrowing was due to abnormal tracheal cartilage rings, whereas a 7-month-old male infant had bronchial stenosis induced by an intrabronchial membrane (Fig 6). In this patient, "passage" through the bronchial stenosis was possible only with VT (Fig 6d) and not with FT. Furthermore, focal hyperinflation of the left upper lobe due to obstructive valve mechanism was diagnosed at multidetector CT with VT.
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Figure 3a: CT images in a 4-month-old male infant with inspiratory stridor since birth and dyspnea. (a) VT image shows subtotal stenosis of distal trachea. Multiplanar reformations with (b) coronal and (c) sagittal views reveal brachiocephalic trunk (arrow) crossing ventral wall of trachea.
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Figure 3b: CT images in a 4-month-old male infant with inspiratory stridor since birth and dyspnea. (a) VT image shows subtotal stenosis of distal trachea. Multiplanar reformations with (b) coronal and (c) sagittal views reveal brachiocephalic trunk (arrow) crossing ventral wall of trachea.
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Figure 3c: CT images in a 4-month-old male infant with inspiratory stridor since birth and dyspnea. (a) VT image shows subtotal stenosis of distal trachea. Multiplanar reformations with (b) coronal and (c) sagittal views reveal brachiocephalic trunk (arrow) crossing ventral wall of trachea.
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Figure 4a: CT images in a 4-year-old girl with recurring pulmonary obstruction and persisting infiltrates. (a) VT image shows mild narrowing of distal trachea with ventral compression (arrows). (b) Transverse section shows brachiocephalic trunk (arrow).
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Figure 4b: CT images in a 4-year-old girl with recurring pulmonary obstruction and persisting infiltrates. (a) VT image shows mild narrowing of distal trachea with ventral compression (arrows). (b) Transverse section shows brachiocephalic trunk (arrow).
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Figure 5a: CT images in 11-month-old male infant with inspiratory stridor since birth. (a) VT image shows deformation and stenosis of distal trachea with ventrolateral right-sided compression (arrows). (b) Transverse image depicts presence of double aortic arch with right descending aorta and vascular ring formation resulting in tracheal compression (right arch, arrow; hypoplastic left arch, arrowhead).
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Figure 5b: CT images in 11-month-old male infant with inspiratory stridor since birth. (a) VT image shows deformation and stenosis of distal trachea with ventrolateral right-sided compression (arrows). (b) Transverse image depicts presence of double aortic arch with right descending aorta and vascular ring formation resulting in tracheal compression (right arch, arrow; hypoplastic left arch, arrowhead).
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Figure 6a: CT images in a 7-month-old male infant with mild stridor and recurrent pulmonary infections. VT images show (a) normal configuration of proximal left main bronchus and (b) total occlusion of left upper lobe bronchus (arrow) due to intrabronchial membrane located at dorsal wall of left main bronchus (arrowheads). (c) Transverse reformation shows intraluminal membrane (arrow). (d) VT images of view into distal left upper lobe bronchus beyond the stenosis. Note focal hyperinflation of left upper lobe due to bronchial obstruction with valve mechanism. Green triangle indicates position of virtual endoscope.
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Figure 6b: CT images in a 7-month-old male infant with mild stridor and recurrent pulmonary infections. VT images show (a) normal configuration of proximal left main bronchus and (b) total occlusion of left upper lobe bronchus (arrow) due to intrabronchial membrane located at dorsal wall of left main bronchus (arrowheads). (c) Transverse reformation shows intraluminal membrane (arrow). (d) VT images of view into distal left upper lobe bronchus beyond the stenosis. Note focal hyperinflation of left upper lobe due to bronchial obstruction with valve mechanism. Green triangle indicates position of virtual endoscope.
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Figure 6c: CT images in a 7-month-old male infant with mild stridor and recurrent pulmonary infections. VT images show (a) normal configuration of proximal left main bronchus and (b) total occlusion of left upper lobe bronchus (arrow) due to intrabronchial membrane located at dorsal wall of left main bronchus (arrowheads). (c) Transverse reformation shows intraluminal membrane (arrow). (d) VT images of view into distal left upper lobe bronchus beyond the stenosis. Note focal hyperinflation of left upper lobe due to bronchial obstruction with valve mechanism. Green triangle indicates position of virtual endoscope.
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Figure 6d: CT images in a 7-month-old male infant with mild stridor and recurrent pulmonary infections. VT images show (a) normal configuration of proximal left main bronchus and (b) total occlusion of left upper lobe bronchus (arrow) due to intrabronchial membrane located at dorsal wall of left main bronchus (arrowheads). (c) Transverse reformation shows intraluminal membrane (arrow). (d) VT images of view into distal left upper lobe bronchus beyond the stenosis. Note focal hyperinflation of left upper lobe due to bronchial obstruction with valve mechanism. Green triangle indicates position of virtual endoscope.
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Ten patients had pulmonary infiltrates at multidetector CT with VT; of those, nine had pathologic tracheobronchial findings, whereas a 6-year-old girl had findings of a normal tracheobronchial system at multidetector CT with VT and FT.
Statistical Parameters
In total, multidetector CT with VT depicted 33 true-positive findings, five true-negative findings, six false-negative findings, and one false-positive finding (Fig 1). Based on these numbers, sensitivity and specificity were calculated as 86.8% (95% CI: 73.3%, 94.7%) and 85.7% (95% CI: 44.6%, 99.3%), respectively, whereas PPV and NPV were 97.1% (95% CI: 84.9%, 99.9%) and 54.5% (95% CI: 25.0%, 80.0%), respectively. Overall accuracy was 86.7% (95% CI: 74.3%, 94.0%).
Radiation Dose
Mean effective dose of all examinations was 1.1 mSv (range, 0.5–1.8 mSv). In the subgroup of patients less than 1 year, mean effective dose was 0.8 mSv.
Additional Imaging Findings
Conventional radiographs showed inconclusive findings in 37 of 38 patients with tracheobronchial anomalies. A double aortic arch with an abnormal mediastinal silhouette could be confirmed in one patient. All patients investigated with echocardiography had findings of normal cardiac anatomy. In four patients with proved brachiocephalic trunk and tracheal compression at multidetector CT with VT, an echocardiographic study was performed, which helped confirm the diagnosis in three patients. In both patients with a double aortic arch and tracheal compression due to vascular ring formation, conventional arteriography was performed and helped confirm the diagnosis. The three patients with H-type tracheoesophageal fistula underwent surgical resection after the diagnosis had been confirmed intraoperatively.
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DISCUSSION
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In our study, multidetector CT with VT was found to depict pediatric tracheobronchial pathologic findings with a sensitivity of 86.8%, a PPV of 97.1%, and an overall accuracy of 86.7%. Abnormal mediastinal vessels and concomitant airway compression were correctly identified in patients at multidetector CT with VT. Furthermore, all congenital airway abnormalities, including accessory bronchi, abnormal bronchial branching, and tracheoesophageal fistulas, were depicted with multidetector CT with VT. However, a substantial number of cases of verified tracheobronchomalacia and relevant functional airway narrowing were not diagnosed at multidetector CT with VT.
As our numbers indicate, congenital vascular abnormalities may account for a substantial number of fixed tracheobronchial stenoses in children. Furthermore, our patient group indicates that tracheal compression due to the brachiocephalic trunk is a problem predominantly affecting patients in the 1st year of life. This probably indicates that the combination of the rise of the vessel from the aortic arch and a "crowded mediastinum" with a large or aberrant thymus are pathophysiologically relevant (18,19).
A major advantage of VT when compared with FT is its noninvasiveness; the method can be used in children who are not able to undergo or whose parents refuse conventional endoscopy. Furthermore, VT can depict passage through high-grade stenoses, which enables evaluation of the poststenotic airway segments (12), as in one patient in our study group. Finally, VT can be complementary to FT in the setting of interventions, including stent implantation, tracheotomy, or partial lung resection. Disadvantages of VT include the inability to perform biopsies and therapeutic maneuvers and that color representation of mucosal surface in VT is artificial. The interpretation of VT images and the detection of pediatric tracheobronchial anomalies requires knowledge of the anatomy of the tracheobronchial tree; we suggest analysis of the images with a chest radiologist and an experienced pediatric pulmonologist.
In our patient group, we used a low-dose protocol with reduction of tube current and voltage. Collimation was chosen on the basis of our experiences and was adjusted to age and weight of the patient. We think that a collimation of less than 1 mm is particularly needed in patients less than 1 year to acquire thin-section images. Considering that guideline values for effective dose at thoracic multidetector CT in adult patients are 11.6 mSv in men and 15.4 mSv in women (20), our results indicate that by using a low-dose protocol, substantial reduction of radiation exposure with a mean effective dose of 1.1 mSv is attainable.
Magnetic resonance (MR) imaging is an alternative imaging modality for the identification of tracheobronchial stenoses and abnormalities (21–23). Results of several studies (24–27) have shown that MR imaging may adequately display mediastinal structures and pathologic findings even in newborns and infants. Advantages of the method are lack of radiation exposure, high soft-tissue contrast, and the ability to perform functional studies (eg, to comparatively evaluate the tracheobronchial system in inspiration and expiration) (28,29). However, even with state-of-the-art MR imaging, spatial resolution at MR imaging is inferior to that at multidetector CT. Furthermore, because of the length of examination time, children often have to be sedated for the acquisition of images of diagnostic quality. In our study group, no patients underwent sedation at multidetector CT scanning, which reflects the clinical tendency expressed in articles (30–32).
VT is possible without administration of contrast material. However, because abnormal vessels constitute a substantial proportion of causes of tracheobronchial stenoses in our patient group and to avoid repeated examination, it seems advisable to perform multidetector CT with contrast enhancement. Intravenous contrast agents used at multidetector CT angiography can be administered with a power injector or with manual injection. Although a power injection is considered a safe tool in pediatric radiology (33) and offers uniformity of enhancement and precise determination of contrast material delivery, we preferred to use manual injection.
In our study group, NPV was low; there were five false-negative findings with multidetector CT with VT (patients with tracheobronchomalacia and normal findings at multidetector CT with VT). This can be explained by the fact that tracheomalacia and bronchomalacia do not account for fixed narrowing and therefore can be reliably diagnosed only at functional studies. The CT examinations in our study group were performed with an inspiratory breath hold, thus causing underestimation of possible airway stenoses due to malacia. The only way to solve this dilemma with multidetector CT would be biphasic examination with inspiration and expiration, which may lead to additional radiation exposure. However, biphasic examination may be performed by limiting the covered volume imaged at the expiratory acquisition.
A possible limitation of our study was the preselection of patients by evaluating their history and physical examination results; patients had a high pretest probability for the presence of tracheobronchial anomalies. Although the radiologists were blinded to the findings of all clinical evaluations and imaging studies, including FT, the results of our study would have probably been different with a more heterogeneous patient population. Our study group included only one patient with normal findings with both image modalities. It would have been desirable in a statistical sense to include more patients without pathologic findings within the mediastinum and the tracheobronchial system. This is, however, difficult to achieve in a prospective manner for ethical reasons. Another limitation was that we did not compare the value of VT images with that of transverse CT images but only with that of FT images. Comparison of VT images and transverse images might have further strengthened the value of virtual endoscopy as an additional tool for thoracic imaging in children. Finally, we used only two scan protocols. A more individual approach, including the use of 100 kVp and between 30 and 60 mA in borderline situations, would have probably made our results more convincing.
In conclusion, the results of our study indicate that multidetector CT with VT can noninvasively depict pediatric tracheobronchial anomalies and stenoses. Specificity, sensitivity, and PPV are high, particularly in patients with vascular anomalies leading to circumscribed airway compression. However, correct diagnostic decision making with VT assumes an experienced reader who is familiar with the anatomy of the pediatric tracheobronchial system. A disadvantage of the method is the inability to depict functional stenoses due to tracheobronchomalacia. Nevertheless, reliable exclusion of other causes of airway compression in symptomatic patients may justify application of multidetector CT with VT even in this subgroup of patients.
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ADVANCES IN KNOWLEDGE
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- Sensitivity and specificity of multidetector CT with virtual tracheobronchoscopy (VT) for depicting airway abnormalities and/or stenoses in pediatric patients is 86.8% and 85.7%, respectively.
- A disadvantage of multidetector CT with VT is the inability to depict functional airway narrowing due to tracheobronchomalacia, which is a common problem in symptomatic pediatric patients.
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FOOTNOTES
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Abbreviations: CI = confidence interval • FT = flexible tracheobronchoscopy • NPV = negative predictive value • PPV = positive predictive value • VT = virtual tracheobronchoscopy
Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, C.M.H.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, C.M.H., D.J., S.A.P., S.P.L., C.H.L.R.; clinical studies, all authors; statistical analysis, C.M.H.; and manuscript editing, all authors
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ABSTRACT
INTRODUCTION
