Nonspecific interstitial pneumonia versus usual interstitial pneumonia: differences in the density histogram of high-resolution CT

J Comput Assist Tomogr. 2005 Jul-Aug;29(4):544-8. doi: 10.1097/01.rct.0000164255.43859.96.


Objective: To assess the capability of the density histogram of high-resolution CT (HRCT) in differentiating nonspecific interstitial pneumonia (NSIP) from usual interstitial pneumonia (UIP) without definite honeycombing.

Methods: Twenty-eight NSIP and 32 UIP patients without definite honeycombing on CT were included in this study. We evaluated a CT image at the level of 1 cm above the diaphragm. The pixels of the lung parenchyma were classified into 4 ranges. The fractions of each range of corresponding density were calculated. The skewness (the degree of asymmetry of a distribution) and kurtosis (how sharply peaked a histogram is) were obtained from the density histogram. The mean value and the mode value of the lung attenuation were also measured.

Results: The fraction of the range of ground-glass opacity and reticular opacity was greater in NSIP patients (32%, 12%) than in UIP patients (23%, 8%) (P < 0.001). UIP had a larger fraction of the range of normal lung. The density histogram was less skewed (P = 0.01) and had a wider peak (P = 0.02) in NSIP (skewness = 1.2879 +/- 0.5672, kurtosis = 1.2115 +/- 1.9470) than in UIP (skewness = 1.6426 +/- 0.4664, kurtosis = 2.3880 +/- 1.8183).

Conclusion: The density histogram reflected the differences in the CT features between NSIP and UIP. Therefore, a density histogram may be helpful for differentiating NSIP from UIP without definite honeycombing.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Diagnosis, Differential
  • Female
  • Humans
  • Lung Diseases, Interstitial / diagnostic imaging*
  • Male
  • Middle Aged
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed