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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

CT images of poly-acryl airway phantom.A. CT image of phantom without tilt angle.B. CT image of phantom tilted at 45° to scan plane. These images were taken with 360-mm reconstruction field of view, B50f reconstruction kernel, and 0.75-mm slice thickness. Note tube shape distortion to ovoid at tilted orientations.
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Figure 1: CT images of poly-acryl airway phantom.A. CT image of phantom without tilt angle.B. CT image of phantom tilted at 45° to scan plane. These images were taken with 360-mm reconstruction field of view, B50f reconstruction kernel, and 0.75-mm slice thickness. Note tube shape distortion to ovoid at tilted orientations.

Mentions: The phantom was scanned at various tilt angles (i.e., 0, 30, 45, and 60°), to the axial plane on a 16-multi-detectorrow CT scanner (Siemens Sensation 16, Siemens Medical Solutions, Erlangen, Germany). The CT scan parameters included a 16 × 0.75 mm collimator with 100 effective mAs, a pitch of 1.0 and 120 kVp, a 512 × 512 matrix setting, and a 360-mm field of view (FOV). The CT images were reconstructed using every combination of the following parameters: five different reconstruction kernels (B10f, B30f, B50f, B70f and B80f); tilt angles (0, 30, 45, and 60°) to the axial plane; and slice thicknesses (0.75, 1, and 2 mm) (Fig. 1). A reconstruction kernel of B10f corresponds to a soft reconstruction kernel, as opposed to B50f, which is standard, and B80f, which is a sharp reconstruction kernel. The resulting 2D image data were stored in the Digital Imaging and Communications in Medicine (DICOM) format.


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)

CT images of poly-acryl airway phantom.A. CT image of phantom without tilt angle.B. CT image of phantom tilted at 45° to scan plane. These images were taken with 360-mm reconstruction field of view, B50f reconstruction kernel, and 0.75-mm slice thickness. Note tube shape distortion to ovoid at tilted orientations.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: CT images of poly-acryl airway phantom.A. CT image of phantom without tilt angle.B. CT image of phantom tilted at 45° to scan plane. These images were taken with 360-mm reconstruction field of view, B50f reconstruction kernel, and 0.75-mm slice thickness. Note tube shape distortion to ovoid at tilted orientations.
Mentions: The phantom was scanned at various tilt angles (i.e., 0, 30, 45, and 60°), to the axial plane on a 16-multi-detectorrow CT scanner (Siemens Sensation 16, Siemens Medical Solutions, Erlangen, Germany). The CT scan parameters included a 16 × 0.75 mm collimator with 100 effective mAs, a pitch of 1.0 and 120 kVp, a 512 × 512 matrix setting, and a 360-mm field of view (FOV). The CT images were reconstructed using every combination of the following parameters: five different reconstruction kernels (B10f, B30f, B50f, B70f and B80f); tilt angles (0, 30, 45, and 60°) to the axial plane; and slice thicknesses (0.75, 1, and 2 mm) (Fig. 1). A reconstruction kernel of B10f corresponds to a soft reconstruction kernel, as opposed to B50f, which is standard, and B80f, which is a sharp reconstruction kernel. The resulting 2D image data were stored in the Digital Imaging and Communications in Medicine (DICOM) format.

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