title: Can a dual-energy computed tomography predict unsuitable stone components for extracorporeal shock wave lithotripsy?
abstract: OBJECTIVE
  To assess the potential of dual-energy computed tomography (DECT) to identify urinary stone components, particularly uric acid and calcium oxalate monohydrate, which are unsuitable for extracorporeal shock wave lithotripsy (ESWL).
  
  
  METHODS
  This clinical study included 246 patients who underwent removal of urinary stones and an analysis of stone components between November 2009 and August 2013. All patients received preoperative DECT using two energy values (80 kVp and 140 kVp). Hounsfield units (HU) were measured and matched to the stone component.
  
  
  RESULTS
  Significant differences in HU values were observed between uric acid and nonuric acid stones at the 80 and 140 kVp energy values (p<0.001). All uric acid stones were red on color-coded DECT images, whereas 96.3% of the nonuric acid stones were blue. Patients with calcium oxalate stones were divided into two groups according to the amount of monohydrate (calcium oxalate monohydrate group: monohydrate≥90%, calcium oxalate dihydrate group: monohydrate<90%). Significant differences in HU values were detected between the two groups at both energy values (p<0.001).
  
  
  CONCLUSIONS
  DECT improved the characterization of urinary stone components and was a useful method for identifying uric acid and calcium oxalate monohydrate stones, which are unsuitable for ESWL.
authors.affiliation: Department of Urology, Institute of Wonkwang Medical Science, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Sung Hoon
authors.initials: SH
authors.lastname: Ahn
authors.affiliation: Department of Urology, Institute of Wonkwang Medical Science, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Tae Hoon
authors.initials: TH
authors.lastname: Oh
authors.affiliation: Department of Urology, Institute of Wonkwang Medical Science, Wonkwang University School of Medicine, Iksan, Korea.
authors.forename: Ill Young
authors.initials: IY
authors.lastname: Seo
mesh_terms: D000328:Adult; D000368:Aged; D002129:Calcium Oxalate / Q000032:analysis; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging* / Q000628:therapy; D008096:Lithotripsy; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D015900:Radiography, Dual-Energy Scanned Projection; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014514:Ureteral Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging* / Q000628:therapy; D014527:Uric Acid / Q000032:analysis
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid
keywords: Calcium oxalate; Uric acid; Urinary calculi; X-ray computed tomography