title: Value of T2-weighted MR imaging in differentiating low-fat renal angiomyolipomas from other renal tumors.
abstract: BACKGROUND
  Accurate preoperative diagnosis of fat scanty angiomyolipomas is an important clinical issue. By evaluating the low signal intensity of angiomyolipomas in MR T2-weighted images the diagnostic accuracy can be elevated.
  
  
  OBJECTIVE
  To retrospectively assess the usefulness of T2-weighted MR imaging for differentiating low-fat angiomyolipomas (AMLs) from other renal tumors.
  
  
  METHODS
  We retrospectively evaluated 71 patients with surgically proven renal masses (10 AMLs, 57 renal cell carcinomas [RCCs], and four oncocytomas), all of which showed no visible fat as well as gradual enhancement patterns on contrast-enhanced CT. Signal intensity was measured in each renal mass and in the spleen on T2-weighted images, and each signal intensity ratio (SIR) was calculated; SIR values were then compared in the AML and non-AML groups. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic performance of the two parameters for differentiating the two groups.
  
  
  RESULTS
  The SIR values (77 ± 24% vs. 162 ± 79%, p = 0.002) were significantly lower in the AML than in the non-AML group. The area under the ROC curve was 0.926 for SIR. The sensitivity and specificity in the diagnosis of AMLs were 90% and 90.2%, using SIR cut-off of 92.5%.
  
  
  CONCLUSIONS
  Signal intensity measurements on T2-weighted MR images can differentiate AML from non-AML in the kidney.
authors.affiliation: Department of Radiology, Asan Medical Center, University of Ulsan, Korea.
authors.forename: Hyuck Jae
authors.initials: HJ
authors.lastname: Choi
authors.forename: Jeong Kon
authors.initials: JK
authors.lastname: Kim
authors.forename: Hanjong
authors.initials: H
authors.lastname: Ahn
authors.forename: Choung-Soo
authors.initials: CS
authors.lastname: Kim
authors.forename: Mi-Hyun
authors.initials: MH
authors.lastname: Kim
authors.forename: Kyoung-Sik
authors.initials: KS
authors.lastname: Cho
mesh_terms: D018249:Adenoma, Oxyphilic / Q000175:diagnosis* / Q000601:surgery; D000328:Adult; D000368:Aged; D018207:Angiomyolipoma / Q000175:diagnosis* / Q000601:surgery; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000601:surgery; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed