title: Determination of renal stone composition in phantom and patients using single-source dual-energy computed tomography.
abstract: OBJECTIVE
  This study aimed to characterize the urinary tract stones in phantom and patients using single-source dual-energy computed tomography.
  
  
  METHODS
  Twenty stones of pure crystalline composition (uric acid [UA], struvite, cystine, and calcium oxalate monohydrate) were assessed in a phantom and 11 patients (age 39-67 years) with urinary tract stones were evaluated. An initial low-dose unenhanced CT (tube potential, 120 kilovolts [peak]; milliampere range, 150-450; noise index, 26; section thickness, 5 mm) followed by a targeted dual-energy computed tomography acquisition on a single-source dual-energy computed tomography (Discovery CT 750 HDCT, GE) was performed. Uric acid and non-UA stones were defined using a 2-material decomposition (material density-iodine/water) algorithm. The stone effective atomic number (Zeff) was used to subclassify non-UA stones. The stone attenuation (Hounsfield unit) was also studied to determine its performance in predicting the composition. Ex vivo chemical analysis of the stone served as a criterion standard.
  
  
  RESULTS
  Of the 59 verified stones (phantom, 20; patients, 39; mean size, 6 mm), there were 16 UA and 43 non-UA type. The material density images were 100% sensitive and accurate in detecting UA and non-UA stones. The Zeff accurately stratified struvite, cystine, and calcium (calcium oxalate monohydrate) stones in the phantom. In patients, Zeff identified 83% of calcium stones (n = 24), and in stones of mixed type, it resembled dominant composition. The Hounsfield unit measurements alone were 71% sensitive and 69% accurate in detecting the UA stones.
  
  
  CONCLUSIONS
  Single-source dual-energy computed tomography can accurately predict UA and non-UA stone composition in vitro and in vivo. Substratification of non-UA stones of pure composition can be made in vitro and in vivo. In stones of mixed composition, the Zeff values reflect the dominant composition.
authors: Abdominal Imaging and Intervention, Harvard Medical School, Massachusetts General Hospital, Boston, MA 02114, USA. .
authors: Naveen M
authors: NM
authors: Kulkarni
authors: Brian H
authors: BH
authors: Eisner
authors: Daniella F
authors: DF
authors: Pinho
authors: Mukta C
authors: MC
authors: Joshi
authors: Avinash R
authors: AR
authors: Kambadakone
authors: Dushyant V
authors: DV
authors: Sahani
mesh_terms: D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*