J Korean Soc Radiol.  2018 Jan;78(1):1-12. 10.3348/jksr.2018.78.1.1.

Quantitative CT Imaging in Chronic Obstructive Pulmonary Disease: Review of Current Status and Future Challenges

• Cho YH
• Seo JB
• Lee SM
• Lee SM
• Choe J
• Lee D
• Kim N

• KMID: 2399300
• DOI: http://doi.org/10.3348/jksr.2018.78.1.1

Abstract

Chronic Obstructive Pulmonary Disease (COPD) is a complex heterogeneous condition with various clinical and pathologic features. In recent years, technical advances in quantitative CT imaging have generated considerable interest because they can provide a more precise and objective assessment of COPD. Emphysema and small-airway disease, the two major components of COPD, and other comorbidities, including pulmonary vessel alterations, atherosclerosis, cachexia, and osteoporosis, can all be assessed by means of quantitative imaging parameters. Increasing numbers of studies provide promising reports indicating that such parameters are associated with clinical measures of disease severity, respiratory symptoms, COPD exacerbations, and mortality. Despite such optimistic results, there are still many obstacles to using this quantitative technology in everyday practice to manage COPD patients. In this article, we review the current technical status of quantitative CT assessment, emphasizing its clinical implications and limitations. We also discuss present challenges and the potential future role of quantitative CT imaging in assessing COPD.

MeSH Terms

Airway Remodeling
Atherosclerosis
Cachexia
Comorbidity
Emphysema
Evaluation Studies as Topic
Humans
Mortality
Osteoporosis
Pulmonary Disease, Chronic Obstructive*

Figure

• 

  Fig. 1 Quantitative CT measurement of emphysema. A. Visual assessment of coronal reconstructed CT image of a patient with chronic obstructive pulmonary disease reveals emphysema involvement with upper lobe dominancy. B. Using the density mask method with a threshold of -950 HU, areas with HU values lower than the threshold (low attenuation areas%) can be readily quantified, and overlaying of the density mask (shown in green on online figure) allows a more robust assessment of emphysema. C. Most available CT quantification software provides reliable automatic segmentation of the lung, making regional quantification of emphysema possible. HU = Hounsfield unit

• 

  Fig. 2 Quantitative assessment of airways. A. Recent technical advances allow more accurate and robust automatic extractions of airways, with three dimensional volumetric reconstructions. B. Once airways are extracted and target points in the airways are selected, quantitative airway parameters are automatically measured (shown in blue on online figure).

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  Fig. 3 Full-width at half-maximum method and commonly measured airway parameters. A. In the attenuation profile along an outwards flowing ray from the luminal center-point through to the airway wall, the inner and outer airway wall boundaries are assumed halfway to the maximum on the lumen side, and halfway to the minimum on the parenchymal side, respectively. B. Diverse airway parameters can be obtained using quantitative analysis, including wall thickness WA, WT, LA, LD, Pi, and WA%. HU = Hounsfield units, LA = lumen area, LD = lumen diameter, Pi = internal perimeter, WA = wall area, WA% = wall area percentage, WT = wall thickness

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  Fig. 4 Air trapping measurement using a co-registration method. Using an image co-registration technique, expiratory CT images are modified and matched with inspiratory CT images. This technique allows voxel-by-voxel comparisons of attenuation changes between inspiration and expiration, with air trapping being defined as areas with less change in attenuation than the preset threshold (60 Hounsfield units in the example shown above).

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