title: Histogram analysis of whole-lesion enhancement in differentiating clear cell from papillary subtype of renal cell cancer.
abstract: OBJECTIVE
  To compare histogram analysis of voxel-based whole-lesion (WL) enhancement to qualitative assessment and region-of-interest (ROI)-based enhancement analysis in discriminating the renal cell cancer (RCC) subtype clear cell RCC (ccRCC) from papillary RCC (pRCC).
  
  
  METHODS
  In this institutional review board-approved, HIPAA-compliant retrospective study, 73 patients underwent magnetic resonance (MR) imaging prior to surgery for RCC between January 2007 and January 2010. Three-dimensional fat-suppressed T1-weighted gradient-echo corticomedullary phase acquisitions, obtained before and after contrast agent administration, were transferred to a workstation at which automated registration followed by semiautomated segmentation of the RCC was performed. Percent enhancement was computed on a per-voxel basis: (SI(post) - SI(pre))/SI(pre) .100, where SI(pre) and SI(post) indicate signal intensity before and after contrast enhancement, respectively. The WL quantitative parameters of mean, median, and third quartile enhancement and histogram distribution parameters kurtosis and skewness were computed for each lesion. WL enhancement parameters were compared with ROI-based analysis and qualitative assessment with regards to diagnostic accuracy and interreader agreement in differentiating ccRCC from pRCC.
  
  
  RESULTS
  There were 19 pRCCs and 55 ccRCCs at pathologic examination. ccRCC had significantly higher WL mean, median, and third quartile enhancement compared with pRCC and hade significantly lower kurtosis and skewness (all P < .001). Third quartile enhancement had the highest accuracy (94.6%; area under the curve, 0.980) in discriminating ccRCC from pRCC, which was significantly higher than the accuracy of qualitative assessment (86.0%; P = .04) but not significantly higher than that of ROI enhancement (89.2%; P = .52). WL enhancement parameters had higher interreader agreement (κ = 0.91-1.0) compared with ROI enhancement or qualitative assessment (κ = 0.83 and 0.7, respectively) in discriminating ccRCC from pRCC.
  
  
  CONCLUSIONS
  WL enhancement histogram analysis is feasible and can potentially be used to differentiate ccRCC from pRCC with high accuracy.
  
  
  BACKGROUND
  http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12111281/-/DC1.
authors.affiliation: Departments of Radiology and Pathology, New York University Langone Medical Center, 550 First Ave, HW201, New York, NY 10016, USA. hersh.chandarana@nyumc.org
authors.forename: Hersh
authors.initials: H
authors.lastname: Chandarana
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Rosenkrantz
authors.forename: Thais C
authors.initials: TC
authors.lastname: Mussi
authors.forename: Sooah
authors.initials: S
authors.lastname: Kim
authors.forename: Afshan A
authors.initials: AA
authors.lastname: Ahmad
authors.forename: Sean D
authors.initials: SD
authors.lastname: Raj
authors.forename: John
authors.initials: J
authors.lastname: McMenamy
authors.forename: Jonathan
authors.initials: J
authors.lastname: Melamed
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
authors.forename: Berthold
authors.initials: B
authors.lastname: Kiefer
authors.forename: Atilla P
authors.initials: AP
authors.lastname: Kiraly
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D002291:Carcinoma, Papillary / Q000175:diagnosis* / Q000473:pathology; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000473:pathology; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D021621:Imaging, Three-Dimensional; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology; D016015:Logistic Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010363:Pattern Recognition, Automated; D015203:Reproducibility of Results; D012189:Retrospective Studies; D018709:Statistics, Nonparametric
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA