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


CONCLUSIONS
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.
Do
Kyung-Hyun
KH
Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
Lee
Jin Seong
JS
Colby
Thomas V
TV
Kitaichi
Masanori
M
Kim
Dong Soon
DS
D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed