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Semi-automatic measurement of the airway dimension by computed tomography using the full-with-half-maximum method: a study of the measurement accuracy according to the orientation of an artificial airway.

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

Bottom Line: A sharper reconstruction kernel, thicker image thickness and larger tilt angle of the airway axis resulted in a significant decrease of the measured wall thickness and an increase of the measured luminal radius.Use of a standard kernel and a 0.75-mm slice thickness resulted in the most accurate measurement of airway dimension, which was independent of obliquity.For the accurate measurement of airway thickness, the CT images should be reconstructed with a standard kernel and a 0.75 mm slice thickness.

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 develop an algorithm to measure the dimensions of an airway oriented obliquely on a volumetric CT, as well as assess the effect of the imaging parameters on the correct measurement of the airway dimension.

Materials and methods: An airway phantom with 11 poly-acryl tubes of various lumen diameters and wall thicknesses was scanned using a 16-MDCT (multidetector CT) at various tilt angles (0, 30, 45, and 60 degrees ). The CT images were reconstructed at various reconstruction kernels and thicknesses. The axis of each airway was determined using the 3D thinning algorithm, with images perpendicular to the axis being reconstructed. The luminal radius and wall thickness was measured by the full-width-half-maximum method. The influence of the CT parameters (the size of the airways, obliquity on the radius and wall thickness) was assessed by comparing the actual dimension of each tube with the estimated values.

Results: The 3D thinning algorithm correctly determined the axis of the oblique airway in all tubes (mean error: 0.91 +/- 0.82 degrees ). A sharper reconstruction kernel, thicker image thickness and larger tilt angle of the airway axis resulted in a significant decrease of the measured wall thickness and an increase of the measured luminal radius. Use of a standard kernel and a 0.75-mm slice thickness resulted in the most accurate measurement of airway dimension, which was independent of obliquity.

Conclusion: The airway obliquity and imaging parameters have a strong influence on the accuracy of the airway wall measurement. For the accurate measurement of airway thickness, the CT images should be reconstructed with a standard kernel and a 0.75 mm slice thickness.

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Related in: MedlinePlus

Interaction of obliquity and reconstruction kernel in accurate measurement of luminal radius. Images were reconstructed at 0.75 mm wall thickness. When sharper reconstruction kernel is used and airway is tilted to larger angle, estimated radius becomes smaller than actual luminal radius. Hence, measurement of reconstructed CT images, using standard kernel (B50f) results in most accurate measurement, independent of obliquity of airway.
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Figure 7: Interaction of obliquity and reconstruction kernel in accurate measurement of luminal radius. Images were reconstructed at 0.75 mm wall thickness. When sharper reconstruction kernel is used and airway is tilted to larger angle, estimated radius becomes smaller than actual luminal radius. Hence, measurement of reconstructed CT images, using standard kernel (B50f) results in most accurate measurement, independent of obliquity of airway.

Mentions: Figure 7 shows the interaction between the airway obliquity and the reconstruction kernel in the measurement of the airway luminal radius. When a sharper reconstruction kernel was used and the airway was tilted to a larger angle, the estimated radius became smaller than the actual radius (Fig. 5). A statistically significant internal interaction between the reconstruction kernel and the obliquity of an airway was observed at the different the tilt angles (p < 0.001). The measurement of the luminal radius was independent of the airway obliquity. The standard kernel (B50f) yielded the most accurate results.


Semi-automatic measurement of the airway dimension by computed tomography using the full-with-half-maximum method: a study of the measurement accuracy according to the orientation of an artificial airway.

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

Interaction of obliquity and reconstruction kernel in accurate measurement of luminal radius. Images were reconstructed at 0.75 mm wall thickness. When sharper reconstruction kernel is used and airway is tilted to larger angle, estimated radius becomes smaller than actual luminal radius. Hence, measurement of reconstructed CT images, using standard kernel (B50f) results in most accurate measurement, independent of obliquity of airway.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2627256&req=5

Figure 7: Interaction of obliquity and reconstruction kernel in accurate measurement of luminal radius. Images were reconstructed at 0.75 mm wall thickness. When sharper reconstruction kernel is used and airway is tilted to larger angle, estimated radius becomes smaller than actual luminal radius. Hence, measurement of reconstructed CT images, using standard kernel (B50f) results in most accurate measurement, independent of obliquity of airway.
Mentions: Figure 7 shows the interaction between the airway obliquity and the reconstruction kernel in the measurement of the airway luminal radius. When a sharper reconstruction kernel was used and the airway was tilted to a larger angle, the estimated radius became smaller than the actual radius (Fig. 5). A statistically significant internal interaction between the reconstruction kernel and the obliquity of an airway was observed at the different the tilt angles (p < 0.001). The measurement of the luminal radius was independent of the airway obliquity. The standard kernel (B50f) yielded the most accurate results.

Bottom Line: A sharper reconstruction kernel, thicker image thickness and larger tilt angle of the airway axis resulted in a significant decrease of the measured wall thickness and an increase of the measured luminal radius.Use of a standard kernel and a 0.75-mm slice thickness resulted in the most accurate measurement of airway dimension, which was independent of obliquity.For the accurate measurement of airway thickness, the CT images should be reconstructed with a standard kernel and a 0.75 mm slice thickness.

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 develop an algorithm to measure the dimensions of an airway oriented obliquely on a volumetric CT, as well as assess the effect of the imaging parameters on the correct measurement of the airway dimension.

Materials and methods: An airway phantom with 11 poly-acryl tubes of various lumen diameters and wall thicknesses was scanned using a 16-MDCT (multidetector CT) at various tilt angles (0, 30, 45, and 60 degrees ). The CT images were reconstructed at various reconstruction kernels and thicknesses. The axis of each airway was determined using the 3D thinning algorithm, with images perpendicular to the axis being reconstructed. The luminal radius and wall thickness was measured by the full-width-half-maximum method. The influence of the CT parameters (the size of the airways, obliquity on the radius and wall thickness) was assessed by comparing the actual dimension of each tube with the estimated values.

Results: The 3D thinning algorithm correctly determined the axis of the oblique airway in all tubes (mean error: 0.91 +/- 0.82 degrees ). A sharper reconstruction kernel, thicker image thickness and larger tilt angle of the airway axis resulted in a significant decrease of the measured wall thickness and an increase of the measured luminal radius. Use of a standard kernel and a 0.75-mm slice thickness resulted in the most accurate measurement of airway dimension, which was independent of obliquity.

Conclusion: The airway obliquity and imaging parameters have a strong influence on the accuracy of the airway wall measurement. For the accurate measurement of airway thickness, the CT images should be reconstructed with a standard kernel and a 0.75 mm slice thickness.

Show MeSH
Related in: MedlinePlus