J Korean Soc Radiol.  2012 Nov;67(5):341-348. 10.3348/jksr.2012.67.5.341.

CT Densitometry of the Lung in Healthy Nonsmokers with Normal Pulmonary Function

• Oh TS
• Chae EJ
• Seo JB
• Jung YJ
• Oh YM
• Lee SD

• KMID: 1819749
• DOI: http://doi.org/10.3348/jksr.2012.67.5.341

Abstract

PURPOSE
To investigate the upper normal limit of low attenuation area% in healthy nonsmokers.
MATERIALS AND METHODS
A total of 36 nonsmokers with normal pulmonary function test underwent a CT scan. Six thresholds (-980 - -930 HU) on inspiration CT and two thresholds (-950 and -910 HU) on expiration CT were used for obtaining low attenuation area%. The mean lung density was obtained on both inspiration CT and expiration CT. Descriptive statistics of low attenuation area% and the mean lung density, evaluation of difference of low attenuation area% and the mean lung density in both sex and age groups, analysis of the relationship between demographic information and CT parameters were performed.
RESULTS
Upper normal limit for low attenuation area% was 12.96% on inspiration CT (-950 HU) and 9.48% on expiration CT (-910 HU). Upper normal limit for the mean lung density was -837.58 HU on inspiration CT and 686.82 HU on expiration CT. Low attenuation area% and the mean lung density showed no significant differences in both sex and age groups. Body mass index (BMI) was negatively correlated with low attenuation area% on inspiration CT (-950 HU, r = -0.398, p = 0.016) and positively correlated with the mean lung density on inspiration CT (r = 0.539, p = 0.001) and expiration CT (r = 0.432, p = 0.009). Age and body surface area were not correlated with low attenuation area% or the mean lung density.
CONCLUSION
Low attenuation area% on CT densitometry of the lung could be found in healthy nonsmokers with normal pulmonary function, and showed negative association with BMI. Reference values, such as range and upper normal limit for low attenuation area% in healthy subjects could be helpful in quantitative analysis and follow up of early emphysema, using CT densitometry of the lung.

MeSH Terms

Body Mass Index
Body Surface Area
Densitometry
Emphysema
Follow-Up Studies
Humans
Lung
Pulmonary Disease, Chronic Obstructive
Reference Values
Respiratory Function Tests
Tomography, X-Ray Computed

Figure

• 

  Fig. 1 Box and whisker plot of low attenuation area (%) along each thresholds on inspiratory CT (A) and expiratory CT (B). Note.-central line = median, ends of boxes = interquartile boundaries, whiskers = data point closest to inner fence (1.5 × interquartile range), • = mild outlier, * = severe outlier, HU = Hounsfield unit, LAA (%) = low attenuation area %

• 

  Fig. 2 Example of quantitative densitometry in a patient with mild emphysema and a healthy subject. A. A 54-year-old male who have mild degree of centrilobular emphysema. A coronal CT image (window level: -750 HU, width: 1500 HU) shows some areas of centrilobular emphysema in both upper lobes. Low attenuation area (%) is shown on a color-coded image demonstrating pixels having CT density below the threshold -950 HU and the value was 4.01%. B. A 59-year-old male who is one of healthy nonsmokers in this study. Emphysema is not evident on a coronal CT image (window level: -750 HU, width: 1500 HU). However, on a color-coded image, there are color-coded areas representing low attenuation area at -950 HU which value was 13.45%.

• 

  Fig. 3 Correlation between low attenuation area (%) at -950 HU on inspiration and body mass index. Note.-BMI = body mass index, LAA (%) = low attenuation area %

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