title: MR imaging of renal cortical tumours: qualitative and quantitative chemical shift imaging parameters.
abstract: OBJECTIVE
  To assess qualitative and quantitative chemical shift MRI parameters of renal cortical tumours.
  
  
  METHODS
  A total of 251 consecutive patients underwent 1.5-T MRI before nephrectomy. Two readers (R1, R2) independently evaluated all tumours visually for a decrease in signal intensity (SI) on opposed- compared with in-phase chemical shift images. In addition, SI was measured on in- and opposed-phase images (SI(IP), SI(OP)) and the chemical shift index was calculated as a measure of percentage SI change. Histopathology served as the standard of reference.
  
  
  RESULTS
  A visual decrease in SI was identified significantly more often in clear cell renal cell carcinoma (RCCs) (R1, 73 %; R2, 64 %) and angiomyolipomas (both, 80 %) than in oncocytomas (29 %, 12 %), papillary (29 %, 17 %) and chromophobe RCCs (13 %, 9 %; all, P < 0.05). Median chemical shift index was significantly greater in clear cell RCC and angiomyolipoma than in the other histological subtypes (both, P < 0.001). Interobserver agreement was fair for visual (kappa, 0.4) and excellent for quantitative analysis (concordance correlation coefficient, 0.80).
  
  
  CONCLUSIONS
  A decrease in SI on opposed-phase chemical shift images is not an identifying feature of clear cell RCCs or angiomyolipomas, but can also be observed in oncocytomas, papillary and chromophobe RCCs. After excluding angiomyolipomas, a decrease in SI of more than 25 % was diagnostic for clear cell RCCs.
  
  
  CONCLUSIONS
  • Chemical shift MRI offers new information about fat within renal tumours. • Opposed-phase signal decrease can be observed in all renal cortical tumours. • A greater than 25 % decrease in signal appears to be diagnostic for clear cell RCCs.
authors.affiliation: Department of Radiology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue. Radiology Academic Offices, Room C278, New York, NY 10065, USA. karloc@mskcc.org
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Karlo
authors.forename: Olivio F
authors.initials: OF
authors.lastname: Donati
authors.forename: Irene A
authors.initials: IA
authors.lastname: Burger
authors.forename: Junting
authors.initials: J
authors.lastname: Zheng
authors.forename: Chaya S
authors.initials: CS
authors.lastname: Moskowitz
authors.forename: Hedvig
authors.initials: H
authors.lastname: Hricak
authors.forename: Oguz
authors.initials: O
authors.lastname: Akin
mesh_terms: D018249:Adenoma, Oxyphilic / Q000175:diagnosis / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018207:Angiomyolipoma / Q000175:diagnosis / Q000473:pathology; D015992:Body Mass Index; D002291:Carcinoma, Papillary / Q000175:diagnosis / Q000473:pathology; D002292:Carcinoma, Renal Cell / Q000175:diagnosis / Q000473:pathology; D005260:Female; D006801:Humans; D007668:Kidney / Q000473:pathology*; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy / Q000379:methods; D015588:Observer Variation; D055815:Young Adult