Rationale and Objectives
To assess the reproducibility of multidetector-row computed tomography (MDCT)-measured forced expiratory tracheal collapse in healthy volunteers.
Methods and Materials
Fourteen healthy, nonsmoking volunteers (6 males, 8 females, mean age 48.7 ± 13.8 years) underwent repeat imaging 1 year after baseline imaging of tracheal dynamics employing the same scanner and technique (64-MDCT, 40 mAs, 120 kVp, and 0.625 mm detector collimation) with spirometric monitoring of total lung capacity and forced exhalation. Cross-sectional area (CSA) of the trachea was measured 1 cm above the aortic arch at end-inspiration and dynamic expiration, and percentage (%) expiratory reduction in tracheal lumen was calculated. Measurements were compared between baseline (Yr1) and repeat imaging (Yr2) using correlation coefficients and Bland-Altman plots.
Results
Mean end-inspiratory CSA was 255.3 ± 56 mm 2 at Yr1 and 255.1 ± 52 mm 2 at Yr2; mean dynamic expiratory CSA was 125.6 ± 60 mm 2 at Yr1 and 132.1 ± 58 mm 2 at Yr2; and mean % expiratory reduction was 51.7 ± 18% at Yr1 and 48.7 ± 19% at Yr2. Mean differences between Yr1 and Yr2 values were 0.2 mm 2 for end-inspiratory CSA, 6.5 mm 2 for dynamic expiratory CSA, and 3.0% for percentage expiratory reduction. There was excellent correlation between the Yr1 and Yr2 measures of end-inspiratory CSA ( r 2 = 0.97, P < .001), dynamic expiratory CSA ( r 2 = 0.89, P < .001), and % expiratory reduction ( r 2 = 0.86, P < .001).
Conclusion
MDCT measurements of forced expiratory tracheal collapse in healthy volunteers are highly reproducible over time.
Multidetector-row computed tomography (MDCT)-paired end-inspiratory and dynamic expiratory imaging has been increasingly used to evaluate expiratory tracheal dynamics in both health and disease . In particular, this technique has been shown to be comparable to the reference standard of bronchoscopy for diagnosing tracheomalacia and has been used to monitor progression and response to treatment of this condition .
The use of MDCT for monitoring progression and response to treatment is based on an assumption that this method is reproducible over time. However, to our knowledge, this assumption has not been previously tested. Therefore, our purpose was to assess the reproducibility of MDCT-measured dynamic expiratory tracheal collapse.
Materials and methods
Study Population
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Imaging Technique
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Computed Tomography Analysis
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Statistical Analysis
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Results
Study Population
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Table 1
Descriptive Features of the Study Population
Gender 6 males, 8 females Age (y) 49 ± 14 Height (cm) 167 ± 10 Weight (kg) 73 ± 13 FEV1 (% predicted) 105 ± 13 FEV1/FVC (% predicted) 107 ± 8
FEV1, forced expiratory volume in 1 second.
FEV1/FVC, ratio of forced expiratory volume in 1 second to forced vital capacity.
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CSA of Tracheal Lumen
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Table 2
Comparison of Cross-sectional Area and Percentage Expiratory Collapse between Measurements at Year 1 (Yr1) and Year 2 (Yr2)
Upper Trachea Yr 1 Yr 2 Mean Difference Inspiration (mm 2 ) 255.3 ± 56 255.1 ± 52 −0.2 Expiration (mm 2 ) 125.6 ± 60 132.1 ± 58 −6.5 Dynamic collapse (%) 51.7 ± 18 48.7 ± 19 −3.0
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Percentage Expiratory Tracheal Collapse
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Discussion
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