title: Iodine quantification to distinguish clear cell from papillary renal cell carcinoma at dual-energy multidetector CT: a multireader diagnostic performance study.
abstract: OBJECTIVE
  To investigate whether dual-energy multidetector row computed tomographic (CT) imaging with iodine quantification is able to distinguish between clear cell and papillary renal cell carcinoma ( RCC renal cell carcinoma ) subtypes.
  
  
  METHODS
  In this retrospective, HIPAA-compliant, institutional review board-approved study, 88 patients (57 men, 31 women) with diagnosis of either clear cell or papillary RCC renal cell carcinoma at pathologic analysis, who underwent contrast material-enhanced dual-energy nephrographic phase study between December 2007 and June 2013, were included. Five readers, blinded to pathologic diagnosis, independently evaluated all cases by determining the lesion iodine concentration on color-coded iodine maps. The receiving operating characteristic curve analysis was adopted to estimate the optimal threshold for discriminating between clear cell and papillary RCC renal cell carcinoma , and results were validated by using a leave-one-out cross-validation. Interobserver agreement was assessed by using an intraclass correlation coefficient. The correlation between tumor iodine concentration and tumor grade was investigated.
  
  
  RESULTS
  A tumor iodine concentration of 0.9 mg/mL represented the optimal threshold to discriminate between clear cell and papillary RCC renal cell carcinoma , and it yielded the following: sensitivity, 98.2% (987 of 1005 [95% confidence interval: 97.7%, 98.7%]); specificity, 86.3% (272 of 315 [95% confidence interval: 85.0%, 87.7%]); positive predictive value, 95.8% (987 of 1030 [95% confidence interval: 95.0%, 96.6%]); negative predictive value, 93.7% (272 of 290 [95% confidence interval: 92.8%, 94.7%]); overall accuracy of 95.3% (1259 of 1320 [95% confidence interval: 94.6%, 96.2%]), with an area under the curve of 0.923 (95% confidence interval: 0.913, 0.933). An excellent agreement was found among the five readers in measured tumor iodine concentration (intraclass correlation coefficient, 0.9990 [95% confidence interval: 0. 9987, 0.9993). A significant correlation was found between tumor iodine concentration and tumor grade for both clear cell (τ = 0.85; P < .001) and papillary RCC renal cell carcinoma (τ = 0.53; P < .001).
  
  
  CONCLUSIONS
  Dual-energy multidetector CT with iodine quantification can be used to distinguish between clear cell and papillary RCC renal cell carcinoma , and it provides insights regarding the tumor grade.
authors.affiliation: From the Department of Radiology, Duke University Medical Center, Box 3808 Erwin Rd, Durham, NC 27710 (A.M., D.M.); Department of Biomedical Sciences and Morphologic and Functional Imaging, Policlinico G. Martino, University of Messina, Messina, Italy (A.M., E.S., A.B., S.M., G.A.); Department of Statistics, North Carolina State University, Raleigh, NC (M.A.C.); and Siemens Medical Solutions USA, Malvern, Pa (J.C.R.G., C.D.E.).
authors.forename: Achille
authors.initials: A
authors.lastname: Mileto
authors.forename: Daniele
authors.initials: D
authors.lastname: Marin
authors.forename: Marcela
authors.initials: M
authors.lastname: Alfaro-Cordoba
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Ramirez-Giraldo
authors.forename: Christian D
authors.initials: CD
authors.lastname: Eusemann
authors.forename: Emanuele
authors.initials: E
authors.lastname: Scribano
authors.forename: Alfredo
authors.initials: A
authors.lastname: Blandino
authors.forename: Silvio
authors.initials: S
authors.lastname: Mazziotti
authors.forename: Giorgio
authors.initials: G
authors.lastname: Ascenti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007479:Iopamidol / Q000031:analogs & derivatives; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography; D009392:Nephrectomy; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media; C057937:iomeprol; D007479:Iopamidol