title: Small (< 4 cm) Renal Masses: Differentiation of Angiomyolipoma Without Visible Fat From Renal Cell Carcinoma Using Unenhanced and Contrast-Enhanced CT.
abstract: OBJECTIVE
  The purpose of this study was to evaluate if small (< 4 cm) angiomyolipoma without visible fat can be differentiated from renal cell carcinoma (RCC) using contrast-enhanced CT alone and using unenhanced and contrast-enhanced CT in combination.
  
  
  METHODS
  Twenty-three patients with 24 angiomyolipomas without visible fat and 130 patients with 148 RCCs underwent unenhanced and contrast-enhanced CT. Demographic data and size, shape, CT attenuation, and heterogeneity (entropy and subjective score) of the renal mass on unenhanced CT and contrast-enhanced CT were recorded. Multivariate logistic regression models were constructed for parameters obtained by contrast-enhanced CT alone and by both unenhanced and contrast-enhanced CT. Demographic data and size and shape of renal mass were used in each model. Sensitivity and specificity were calculated.
  
  
  RESULTS
  Logistic regression model from contrast-enhanced CT data included sex, percentage of exophytic growth, entropy, and CT attenuation on contrast-enhanced CT. Model from both unenhanced and contrast-enhanced CT data included age, sex, short-axis diameter, percentage of exophytic growth, lesion-to-kidney CT attenuation difference on unenhanced CT, and CT attenuation on contrast-enhanced CT. The contrast-enhanced CT-based model and combined unenhanced and contrast-enhanced CT-based model differentiated angiomyolipoma from RCC with sensitivity and specificity of 42% and 98% versus 50% and 98%, respectively.
  
  
  CONCLUSIONS
  Combinations of various CT and demographic findings allowed differentiation of angiomyolipoma from RCC.
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Naoki
authors.initials: N
authors.lastname: Takahashi
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Shuai
authors.initials: S
authors.lastname: Leng
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.|2 Present address: Department of Radiology, Kobe University, Faculty of Medicine, Hyogo, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kitajima
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.|3 Present address: Department of Medical Physics, School of Medicine, University of Wisconsin, Madison, WI.
authors.forename: Daniel
authors.initials: D
authors.lastname: Gomez-Cardona
authors.affiliation: 4 Department of Health Sciences Research, Mayo Clinic, Rochester, MN.
authors.forename: Prabin
authors.initials: P
authors.lastname: Thapa
authors.affiliation: 4 Department of Health Sciences Research, Mayo Clinic, Rochester, MN.
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.affiliation: 5 Department of Urology, Mayo Clinic, Rochester, MN.
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Leibovich
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.|6 Present address: Department of Radiology, Faculty of Medicine, King Chulalongkorn Memorial Hospital, Chulalongkorn University, Bangkok, Thailand.
authors.forename: Kewalee
authors.initials: K
authors.lastname: Sasiwimonphan
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.|7 Present address: Department of Radiology, Faculty of Medicine, Saga University, Saga, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Sasaguri
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Akira
authors.initials: A
authors.lastname: Kawashima
mesh_terms: D000328:Adult; D000368:Aged; D018207:Angiomyolipoma / Q000000981:diagnostic imaging* / Q000473:pathology; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging* / Q000473:pathology; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media
keywords: CT; angiomyolipoma; kidney; renal cell carcinoma; texture analysis