title: Fragility of brushite stones in shock wave lithotripsy: absence of correlation with computerized tomography visible structure.
abstract: OBJECTIVE
  Brushite stones were imaged in vitro and then broken with shock wave lithotripsy to assess whether stone fragility correlates with internal stone structure visible on helical computerized tomography.
  
  
  METHODS
  A total of 52 brushite calculi were scanned by micro computerized tomography, weighed, hydrated and placed in a radiological phantom. Stones were scanned using a Philips® Brilliance iCT 256 system and images were evaluated for the visibility of internal structural features. The calculi were then treated with shock wave lithotripsy in vitro. The number of shock waves needed to break each stone to completion was recorded.
  
  
  RESULTS
  The number of shock waves needed to break each stone normalized to stone weight did not differ by HU value (p = 0.84) or by computerized tomography visible structures that could be identified consistently by all observers (p = 0.053). Stone fragility correlated highly with stone density and brushite content (each p <0.001). Calculi of almost pure brushite required the most shock waves to break. When all observations of computerized tomography visible structures were used for analysis by logistic fit, computerized tomography visible structure predicted increased stone fragility with an overall area under the ROC curve of 0.64.
  
  
  CONCLUSIONS
  The shock wave lithotripsy fragility of brushite stones did not correlate with internal structure discernible on helical computerized tomography. However, fragility did correlate with stone density and increasing brushite mineral content, consistent with clinical experience with patients with brushite calculi. Thus, current diagnostic computerized tomography technology does not provide a means to predict when brushite stones will break well using shock wave lithotripsy.
authors: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120, USA. jwillia3@iupui.edu
authors: James C
authors: JC
authors: Williams
authors: Tariq
authors: T
authors: Hameed
authors: Molly E
authors: ME
authors: Jackson
authors: Syed
authors: S
authors: Aftab
authors: Alessia
authors: A
authors: Gambaro
authors: Yuri A
authors: YA
authors: Pishchalnikov
authors: James E
authors: JE
authors: Lingeman
authors: James A
authors: JA
authors: McAteer
mesh_terms: D002130:Calcium Phosphates; D066298:In Vitro Techniques; D007669:Kidney Calculi / Q000000981:diagnostic imaging* / Q000628:therapy*; D008096:Lithotripsy; D036542:Tomography, Spiral Computed
chemical_list: D002130:Calcium Phosphates; C494366:calcium phosphate, dibasic, dihydrate