title: Dual source computed tomography: a novel technique to determine stone composition.
abstract: BACKGROUND
  Dual source computed tomography (CT), a novel technology that employs two different x-ray sources, may provide an image resolution that has not been possible with conventional single source CT. We tested the ability of dual source CT imaging to distinguish calcium oxalate (CaOx) stones from calcium phosphate (CaP) stones, and both types of calciferous stones from uric acid (UA) stones.
  
  
  METHODS
  CaOx, CaP, and UA stones were placed in a tissue phantom and imaged with dual source multidetector CT at both 80kV and 140 kV. Hounsfield units (HU) of each stone were recorded for the 140 kV and the 80 kV datasets by drawing regions of interest by circle, hand-drawing, and using a volume calculation method. The differences between, and the ratios of, the HU obtained by the two energy sources were compared among the stone groups.
  
  
  RESULTS
  Between CaOx and CaP stones, HU differences (80kV-140kV difference, hand-drawing technique: CaOx = 270.7; CaP = 369.5; UA = 11.45; P = 0.020 for CaOx vs. CaP; P < 0.001 for CaOx and CaP vs. UA) as well as ratios (140kV:80kV ratio, hand-drawing technique: CaOx = 1.44; CaP = 1.51; UA = 1.04; P = 0.001 for CaOx vs. CaP; P < 0.001 for CaOx and CaP vs. UA) were significantly different. There were no significant differences in stone size among the groups.
  
  
  CONCLUSIONS
  Dual source CT has the ability to distinguish not only between calciferous stones and uric acid stones, but also among stones composed of different calcium salts. Further studies are warranted to confirm these findings in a clinical setting.
authors.affiliation: The Russell H Morgan Department of Radiology and Radiological Science, James Buchanan Brady Urological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21209, USA. bmatlaga@jhmi.edu
authors.forename: Brian R
authors.initials: BR
authors.lastname: Matlaga
authors.forename: Satomi
authors.initials: S
authors.lastname: Kawamoto
authors.forename: Elliot
authors.initials: E
authors.lastname: Fishman
mesh_terms: D002129:Calcium Oxalate; D002130:Calcium Phosphates; D003937:Diagnosis, Differential; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging*; D008954:Models, Biological; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*; D014527:Uric Acid
chemical_list: D002130:Calcium Phosphates; D002129:Calcium Oxalate; D014527:Uric Acid; C020243:calcium phosphate