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Semi-automatic measurement of the airway dimension by computed tomography using the full-width-half-maximum method: a study on the measurement accuracy according to the CT parameters and size of the airway.

Kim N, Seo JB, Song KS, Chae EJ, Kang SH - Korean J Radiol (2008 May-Jun)

Bottom Line: The measured values as determined by CT and the actual dimensions of the tubes were compared.There was no significant difference in accuracy among images with the use of variable slice thicknesses or a variable FOV.Below a 1-mm threshold, the measurement failed to represent the change of the real dimensions.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.

ABSTRACT

Objective: To assess the influence of variable factors such as the size of the airway and the CT imaging parameters such as the reconstruction kernel, field-of-view (FOV), and slice thickness on the automatic measurement of airway dimension.

Materials and methods: An airway phantom was fabricated that contained eleven poly-acryl tubes of various lumen diameters and wall thicknesses. The measured density of the poly-acryl wall was 150 HU, and the measured density of the airspace filled with polyurethane foam was -900 HU. CT images were obtained using a 16-MDCT (multidetector CT) scanner and were reconstructed with various reconstruction kernels, thicknesses and FOV. The luminal radius and wall thickness were measured using in-house software based on the full-width-half-maximum method. The measured values as determined by CT and the actual dimensions of the tubes were compared.

Results: Measurements were most accurate on images reconstructed with use of a standard kernel (mean error: -0.03 +/- 0.21 mm for wall thickness and -0.12 +/- 0.11 mm for the luminal radius). There was no significant difference in accuracy among images with the use of variable slice thicknesses or a variable FOV. Below a 1-mm threshold, the measurement failed to represent the change of the real dimensions.

Conclusion: Measurement accuracy was strongly influenced by the specific reconstruction kernel utilized. For accurate measurement, standardization of the imaging protocol and selection of the appropriate anatomic level are essential.

Show MeSH
Effect of reconstruction kernel on accuracy of airway wall measurement. Estimated wall thickness as compared with actual wall thickness (Reference) were determined with use of every reconstruction kernel. All images were reconstructed with 0.75-mm slice thickness and 360-mm field of view parameters.
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Figure 3: Effect of reconstruction kernel on accuracy of airway wall measurement. Estimated wall thickness as compared with actual wall thickness (Reference) were determined with use of every reconstruction kernel. All images were reconstructed with 0.75-mm slice thickness and 360-mm field of view parameters.

Mentions: In cases of the use of the smoother reconstruction kernels (B10f, and B30f), the small airway lumen and wall thickness of the first and second tubes could not be measured. A severe partial volume effect made the profile of these tubes, which have a lumen radius of less than 0.66 mm, unrepresentative of the typical curve of the airway lumen and wall. Therefore, these measurements were treated as missing measurements. In addition, all of the measurements of the first and second tubes were excluded in all statistical tests, as there is a measurement limitation of the spatial resolution of MDCT below a 1-mm wall thickness with the use of the FWHM method (Fig. 3).


Semi-automatic measurement of the airway dimension by computed tomography using the full-width-half-maximum method: a study on the measurement accuracy according to the CT parameters and size of the airway.

Kim N, Seo JB, Song KS, Chae EJ, Kang SH - Korean J Radiol (2008 May-Jun)

Effect of reconstruction kernel on accuracy of airway wall measurement. Estimated wall thickness as compared with actual wall thickness (Reference) were determined with use of every reconstruction kernel. All images were reconstructed with 0.75-mm slice thickness and 360-mm field of view parameters.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2627250&req=5

Figure 3: Effect of reconstruction kernel on accuracy of airway wall measurement. Estimated wall thickness as compared with actual wall thickness (Reference) were determined with use of every reconstruction kernel. All images were reconstructed with 0.75-mm slice thickness and 360-mm field of view parameters.
Mentions: In cases of the use of the smoother reconstruction kernels (B10f, and B30f), the small airway lumen and wall thickness of the first and second tubes could not be measured. A severe partial volume effect made the profile of these tubes, which have a lumen radius of less than 0.66 mm, unrepresentative of the typical curve of the airway lumen and wall. Therefore, these measurements were treated as missing measurements. In addition, all of the measurements of the first and second tubes were excluded in all statistical tests, as there is a measurement limitation of the spatial resolution of MDCT below a 1-mm wall thickness with the use of the FWHM method (Fig. 3).

Bottom Line: The measured values as determined by CT and the actual dimensions of the tubes were compared.There was no significant difference in accuracy among images with the use of variable slice thicknesses or a variable FOV.Below a 1-mm threshold, the measurement failed to represent the change of the real dimensions.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.

ABSTRACT

Objective: To assess the influence of variable factors such as the size of the airway and the CT imaging parameters such as the reconstruction kernel, field-of-view (FOV), and slice thickness on the automatic measurement of airway dimension.

Materials and methods: An airway phantom was fabricated that contained eleven poly-acryl tubes of various lumen diameters and wall thicknesses. The measured density of the poly-acryl wall was 150 HU, and the measured density of the airspace filled with polyurethane foam was -900 HU. CT images were obtained using a 16-MDCT (multidetector CT) scanner and were reconstructed with various reconstruction kernels, thicknesses and FOV. The luminal radius and wall thickness were measured using in-house software based on the full-width-half-maximum method. The measured values as determined by CT and the actual dimensions of the tubes were compared.

Results: Measurements were most accurate on images reconstructed with use of a standard kernel (mean error: -0.03 +/- 0.21 mm for wall thickness and -0.12 +/- 0.11 mm for the luminal radius). There was no significant difference in accuracy among images with the use of variable slice thicknesses or a variable FOV. Below a 1-mm threshold, the measurement failed to represent the change of the real dimensions.

Conclusion: Measurement accuracy was strongly influenced by the specific reconstruction kernel utilized. For accurate measurement, standardization of the imaging protocol and selection of the appropriate anatomic level are essential.

Show MeSH