title: Kurtosis and skewness assessments of solid lung nodule density histograms: differentiating malignant from benign nodules on CT.
abstract: OBJECTIVE
  The purpose of our study was to assess pulmonary nodule characteristics using density histogram kurtosis and skewness and to distinguish malignant from benign nodules.
  
  
  METHODS
  Ninety-three lung nodules on CT were analyzed, including 72 malignant and 21 benign nodules. They were completely solid or solid with limited ground-glass opacity. Based on their CT characteristics, nodules were categorized into type A, homogeneous nodules with uniform internal structures and clear margins, and type B, inhomogeneous nodules with heterogeneous structures or uneven margins. Kurtosis and skewness were calculated from density histograms to compare type A and B nodules and malignant and benign nodules. Receiver-operating characteristic (ROC) curves were generated to assess kurtosis and skewness for discriminating between different nodule types.
  
  
  RESULTS
  Type A nodules (n = 35) had greater kurtosis and reduced skewness (p < 0.001) compared to type B nodules (n = 58). Malignant tumor kurtosis was greater than that of benign nodules (type A, p < 0.05; type B, p = 0.001). Type B malignant tumors had reduced skewness compared to benign nodules (p < 0.05). ROC curves provided relatively high values for the area under the curve (0.71-0.83).
  
  
  CONCLUSIONS
  Kurtosis and skewness assessments of density histograms may be useful for differentiating malignant from benign nodules.
authors.affiliation: Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa, 903-0215, Japan, ayano1242004@yahoo.co.jp.
authors.forename: Ayano
authors.initials: A
authors.lastname: Kamiya
authors.forename: Sadayuki
authors.initials: S
authors.lastname: Murayama
authors.forename: Hisashi
authors.initials: H
authors.lastname: Kamiya
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Yamashiro
authors.forename: Yasuji
authors.initials: Y
authors.lastname: Oshiro
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tanaka
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D012372:ROC Curve; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed