Korean J Radiol.  2011 Apr;12(2):169-175. 10.3348/kjr.2011.12.2.169.

Reconstruction Algorithms Influence the Follow-Up Variability in the Longitudinal CT Emphysema Index Measurements

• Hochhegger B
• Irion KL
• Marchiori
• Moreira JS

• KMID: 1088561
• DOI: http://doi.org/10.3348/kjr.2011.12.2.169

Abstract

OBJECTIVE
We wanted to compare the variability in the longitudinal emphysema index (EI) measurements that were computed with standard and high resolution (HR) reconstruction algorithms (RAs).
MATERIALS AND METHODS
We performed a retrospective review of 475 patients who underwent CT for surveillance of lung nodules. From this cohort, 50 patients (28 male) were included in the study. For these patients, the baseline and follow-up scans were acquired on the same multidetector CT scanner and using the same acquisition protocol. The CT scans were reconstructed with HR and standard RAs. We determined the difference in the EI between CT1 and CT2 for the HR and standard RAs, and we compared the variance of these differences.
RESULTS
The mean of the variation of the total lung volume was 0.14 L (standard deviation [SD] = 0.13 L) for the standard RA and 0.16 L (SD = 0.15 L) for the HR RA. These differences were not significant. For the standard RA, the mean variation was 0.13% (SD = 0.44%) for EI -970 and 0.4% (SD = 0.88%) for EI -950; for the HR RA, the mean variation was 1.9% (SD = 2.2%) for EI -970 and 3.6% (SD = 3.7%) for EI -950. These differences were significant.
CONCLUSION
Using an HR RA appears to increase the variability of the CT measurements of the EI.

Keyword

Reconstruction algorithm; Emphysema; Computed tomography (CT)

MeSH Terms

Aged
Algorithms
Artifacts
Female
Humans
Imaging, Three-Dimensional
Male
Pulmonary Emphysema/*radiography
Radiographic Image Interpretation, Computer-Assisted/*methods
Retrospective Studies
Statistics, Nonparametric
*Tomography, X-Ray Computed

Figure

• 

  Fig. 1 3D CT volume with emphysema volumes in white. A. Reconstruction image with standard algorithm. B. Reconstruction image with high resolution algorithm. Note difference in emphysema volumes.

• 

  Fig. 2 Comparison of differencs in CT measurements of total lung volume at CT1 and CT2 between reconstruction algorithm. A. Comparison of differences in CT measurements of total lung volume (TLV) at CT1 and CT2 between high resolution (HR) reconstruction algorithm (RA) and standard reconstruction algorithm. B. Comparison of differences in CT measurements of mean lung density (MLD) at CT1 and CT2 between high resolution reconstruction algorithm and standard reconstruction algorithm.

• 

  Fig. 3 Comparison of differences in CT measurements of EI -950 at CT1 and CT2 between reconstruction algorithm. A. Comparison of differences in CT measurements of EI -950 at CT1 and CT2 between high resolution (HR) reconstruction algorithm (RA) and standard reconstruction algorithm. B. Comparison of differences in CT measurements of EI -970 at CT1 and CT2 between high resolution reconstruction algorithm and standard reconstruction algorithm.

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