title: The value of "liver windows" settings in the detection of small renal cell carcinomas on unenhanced computed tomography.
abstract: OBJECTIVE
  To assess if "liver window" settings improve the conspicuity of small renal cell carcinomas (RCC).
  
  
  METHODS
  Patients were analysed from our institution's pathology-confirmed RCC database that included the following: (1) stage T1a RCCs, (2) an unenhanced computed tomography (CT) abdomen performed ≤ 6 months before histologic diagnosis, and (3) age ≥ 17 years. Patients with multiple tumours, prior nephrectomy, von Hippel-Lindau disease, and polycystic kidney disease were excluded. The unenhanced CT was analysed, and the tumour locations were confirmed by using corresponding contrast-enhanced CT or magnetic resonance imaging studies. Representative single-slice axial, coronal, and sagittal unenhanced CT images were acquired in "soft tissue windows" (width, 400 Hounsfield unit (HU); level, 40 HU) and liver windows (width, 150 HU; level, 88 HU). In addition, single-slice axial, coronal, and sagittal unenhanced CT images of nontumourous renal tissue (obtained from the same cases) were acquired in soft tissue windows and liver windows. These data sets were randomized, unpaired, and were presented independently to 3 blinded radiologists for analysis. The presence or absence of suspicious findings for tumour was scored on a 5-point confidence scale.
  
  
  RESULTS
  Eighty-three of 415 patients met the study criteria. Receiver operating characteristics (ROC) analysis, t test analysis, and kappa analysis were used. ROC analysis showed statistically superior diagnostic performance for liver windows compared with soft tissue windows (area under the curve of 0.923 vs 0.879; P = .0002). Kappa statistics showed "good" vs "moderate" agreement between readers for liver windows compared with soft tissue windows.
  
  
  CONCLUSIONS
  Use of liver windows settings improves the detection of small RCCs on the unenhanced CT.
authors.affiliation: Department of Radiology and Diagnostic Imaging, University of Alberta Hospital, Edmonton, Alberta, Canada.
authors.forename: Kamal
authors.initials: K
authors.lastname: Sahi
authors.affiliation: Department of Radiology and Diagnostic Imaging, University of Alberta Hospital, Edmonton, Alberta, Canada.
authors.forename: Stuart
authors.initials: S
authors.lastname: Jackson
authors.affiliation: Department of Radiology and Diagnostic Imaging, University of Alberta Hospital, Edmonton, Alberta, Canada.
authors.forename: Edward
authors.initials: E
authors.lastname: Wiebe
authors.affiliation: Department of Radiology and Diagnostic Imaging, University of Alberta Hospital, Edmonton, Alberta, Canada.
authors.forename: Gavin
authors.initials: G
authors.lastname: Armstrong
authors.affiliation: Department of Radiology and Diagnostic Imaging, University of Alberta Hospital, Edmonton, Alberta, Canada.
authors.forename: Sean
authors.initials: S
authors.lastname: Winters
authors.affiliation: Division of Urology, Department of Surgery and Oncology, University of Alberta Hospital, Edmonton, Alberta, Canada.
authors.forename: Ronald
authors.initials: R
authors.lastname: Moore
authors.affiliation: Department of Radiology and Diagnostic Imaging, University of Alberta Hospital, Edmonton, Alberta, Canada. Electronic address: timgy@yahoo.com.
authors.forename: Gavin
authors.initials: G
authors.lastname: Low
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Carcinoma; Diagnostic errors; Diagnostic imaging; Early detection of cancer; Multidetector computed tomography; renal cell