title: Utility of iodine overlay technique and virtual unenhanced images for the characterization of renal masses by dual-energy CT.
abstract: OBJECTIVE
  The objective of our study was to assess the utility of dual-energy CT for characterizing renal masses using iodine overlay techniques and virtual unenhanced images and to measure the potential radiation dose reduction for two-phase kidney CT compared with a standard three-phase protocol.
  
  
  METHODS
  Sixty patients with suspected renal masses underwent dual-energy CT including true unenhanced, dual-energy corticomedullary, and dual-energy late nephrographic phase imaging. Iodine overlay and virtual unenhanced images were derived from the corticomedullary and late nephrographic phases, respectively. The CT numbers of renal masses were calculated using the iodine overlay images superimposed on the virtual unenhanced images. The overall imaging quality of the true unenhanced images and of the virtual unenhanced images was also evaluated. The effective radiation doses for dual-energy CT and for true unenhanced imaging were calculated.
  
  
  RESULTS
  For overlay or enhancement values on iodine overlay images, 36 simple cysts and 10 hemorrhagic cysts had an attenuation value of less than 20 HU, whereas 21 renal cell carcinomas showed an attenuation value of 20 HU or greater. Eleven angiomyolipomas contained macroscopic fat tissue. All renal masses were accurately classified on the basis of dual-energy CT. The imaging quality of the virtual unenhanced images from the corticomedullary and late nephrographic phases was inferior to the image quality of the true unenhanced images (p < 0.01). The mean effective doses for the three-phase protocol and for true unenhanced images were 12.6 and 2.4 mSv, respectively.
  
  
  CONCLUSIONS
  Our results show that dual-energy CT using iodine overlay techniques and virtual unenhanced images may be useful for characterizing renal masses.
authors: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Kangnam-gu, Seoul, Republic of Korea.
authors: Kyoung Doo
authors: KD
authors: Song
authors: Chan Kyo
authors: CK
authors: Kim
authors: Byung Kwan
authors: BK
authors: Park
authors: Bohyun
authors: B
authors: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003287:Contrast Media; D005260:Female; D006801:Humans; D007479:Iopamidol / Q000031:analogs & derivatives*; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011856:Radiographic Image Enhancement / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; C057937:iomeprol; D007479:Iopamidol