title: Determining the composition of urinary tract calculi using stone-targeted dual-energy CT: evaluation of a low-dose scanning protocol in a clinical environment.
abstract: OBJECTIVE
  This study will evaluate the accuracy of dual-energy CT (DECT) in characterizing urinary tract stone composition on patients presenting to a UK hospital with renal colic. The study will also assess the additional radiation dose burden of DECT over standard protocol.
  
  
  METHODS
  Data from 106 DECTs between October 2011 and October 2015 were retrospectively analyzed. Patients were imaged using a Toshiba Aquilion ONE™CT scanner (Toshiba Medical Systems, Otawara-shi, Japan). All patients received a low-dose non-contrast CT of the abdomen and pelvis prior to stone-targeted DECT at 80 and 135 kVp and 40-mm field of view. Radiation dose output was evaluated using dose-length product (DLP). 19 stones were recovered and their compositions were analyzed using Fourier transform infrared spectroscopy.
  
  
  RESULTS
  137 stones were characterized. Mean stone diameter was 8.8 mm (range 3-48 mm). There was an 18.7% increase in mean DLP for DECT over standard CT protocol (319.4 vs 269.1 mGy cm; p < 0.001). Infrared spectroscopy analysis of 19 recovered stones identified 15 stones as calcium, 2 stones as cystine and 2 stones as mixed composition. Dual energy correctly predicted 11 (78.6%) of 14 calcium stones, 2 (100%) of 2 mixed composition stones and 0 (0%) of 2 cystine stones, resulting in a fair agreement (Cohen's κ = 0.374, p = 0.009).
  
  
  CONCLUSIONS
  DECT is able to determine the composition of urinary tract stones with fair accuracy. Its utility is offset by a small but significant supplementary radiation exposure. Advances in knowledge: DECT can provide urological surgeons with useful diagnostic stone material information prior to planning optimal management of stone disease.
authors: 1 Department of Urology, Morriston Hospital, Swansea, UK.
authors: Richard J
authors: RJ
authors: Chaytor
authors: 1 Department of Urology, Morriston Hospital, Swansea, UK.
authors: Krishnamoorthy
authors: K
authors: Rajbabu
authors: 1 Department of Urology, Morriston Hospital, Swansea, UK.
authors: Paul A
authors: PA
authors: Jones
authors: 2 Department of Radiology, Morriston Hospital, Swansea, UK.
authors: Liam
authors: L
authors: McKnight
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D056844:Renal Colic / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D017550:Spectroscopy, Fourier Transform Infrared; D014057:Tomography, X-Ray Computed / Q000379:methods*; D006113:United Kingdom; D014545:Urinary Calculi / Q000737:chemistry* / Q000000981:diagnostic imaging*
chemical_list: D003287:Contrast Media