title: Quantitative Prediction of Stone Fragility From Routine Dual Energy CT: Ex vivo proof of Feasibility.
abstract: Previous studies have demonstrated a qualitative relationship between stone fragility and internal stone morphology. The goal of this study was to quantify morphologic features from dual-energy computed tomography (CT) images and assess their relationship to stone fragility.
  
  
  
  Thirty-three calcified urinary stones were scanned with micro-CT. Next, they were placed within torso-shaped water phantoms and scanned with the dual-energy CT stone composition protocol in routine use at our institution. Mixed low- and high-energy images were used to measure volume, surface roughness, and 12 metrics describing internal morphology for each stone. The ratios of low- to high-energy CT numbers were also measured. Subsequent to imaging, stone fragility was measured by disintegrating each stone in a controlled ex vivo experiment using an ultrasonic lithotripter and recording the time to comminution. A multivariable linear regression model was developed to predict time to comminution.
  
  
  
  The average stone volume was 300 mm3(range: 134-674 mm3). The average comminution time measured ex vivo was 32 seconds (range: 7-115 seconds). Stone volume, dual-energy CT number ratio, and surface roughness were found to have the best combined predictive ability to estimate comminution time (adjusted R2= 0.58). The predictive ability of mixed dual-energy CT images, without use of the dual-energy CT number ratio, to estimate comminution time was slightly inferior, with an adjusted R2of 0.54.
  
  
  
  Dual-energy CT number ratios, volume, and morphologic metrics may provide a method for predicting stone fragility, as measured by time to comminution from ultrasonic lithotripsy.
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ferrero
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Montoya
authors.affiliation: Department of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota.
authors.forename: Lisa E
authors.initials: LE
authors.lastname: Vaughan
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Alice E
authors.initials: AE
authors.lastname: Huang
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
authors.forename: Ian O
authors.initials: IO
authors.lastname: McKeag
authors.affiliation: Department of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota.
authors.forename: Felicity T
authors.initials: FT
authors.lastname: Enders
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: James C
authors.initials: JC
authors.lastname: Williams
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Electronic address: mccollough.cynthia@mayo.edu.
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
mesh_terms: D004867:Equipment Design; D005240:Feasibility Studies; D006801:Humans; D008096:Lithotripsy / Q000295:instrumentation / Q000379:methods; D019047:Phantoms, Imaging; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods; D014545:Urinary Calculi / Q000000981:diagnostic imaging* / Q000473:pathology / Q000628:therapy
keywords: Kidney calculi; Lithotripsy; X-ray computed tomography