title: Automated analysis of urinary stone composition using Raman spectroscopy: pilot study for the development of a compact portable system for immediate postoperative ex vivo application.
abstract: OBJECTIVE
  We evaluate a compact portable system for immediate automated postoperative ex vivo analysis of urinary stone composition using Raman spectroscopy. Analysis of urinary stone composition provides essential information for the treatment and metaphylaxis of urolithiasis. Currently infrared spectroscopy and x-ray diffraction are used for urinary stone analysis. However, these methods may require complex sample preparation and costly laboratory equipment. In contrast, Raman spectrometers could be a simple and quick strategy for immediate stone analysis.
  
  
  METHODS
  Pure samples of 9 stone components and 159 human urinary calculi were analyzed by Raman spectroscopy using a microscope coupled system at 2 excitation wavelengths. Signal-to-noise ratio, peak positions and the distinctness of the acquired Raman spectra were analyzed and compared. Background fluorescence was removed mathematically. Corrected Raman spectra were used as a reference library for automated classification of native human urinary stones (50). The results were then compared to standard infrared spectroscopy.
  
  
  RESULTS
  Signal-to-noise ratio was superior at an excitation wavelength of 532 nm. An automated, computer based classifier was capable of matching spectra from patient samples with those of pure stone components. Consecutive analysis of 50 human stones demonstrated 100% sensitivity and specificity compared to infrared spectroscopy (for components with more than 25% of total composition).
  
  
  CONCLUSIONS
  Our pilot study indicates that Raman spectroscopy is a valid and reliable technique for determining urinary stone composition. Thus, we propose that the development of a compact and portable system based on Raman spectroscopy for immediate, postoperative stone analysis could represent an invaluable tool for the metaphylaxis of urolithiasis.
authors.affiliation: Department of Urology, University Medical Centre Freiburg, Freiburg, Germany; Fraunhofer Institute for Physical Measurement Techniques, Freiburg, Germany. Electronic address: arkadiusz.miernik@uniklinik-freiburg.de.
authors.forename: Arkadiusz
authors.initials: A
authors.lastname: Miernik
authors.forename: Yvan
authors.initials: Y
authors.lastname: Eilers
authors.forename: Carsten
authors.initials: C
authors.lastname: Bolwien
authors.forename: Armin
authors.initials: A
authors.lastname: Lambrecht
authors.forename: Dieter
authors.initials: D
authors.lastname: Hauschke
authors.forename: Gunter
authors.initials: G
authors.lastname: Rebentisch
authors.forename: Phillipp S
authors.initials: PS
authors.lastname: Lossin
authors.forename: Albrecht
authors.initials: A
authors.lastname: Hesse
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Rassweiler
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wetterauer
authors.forename: Martin
authors.initials: M
authors.lastname: Schoenthaler
mesh_terms: D004867:Equipment Design; D006801:Humans; D010865:Pilot Projects; D011182:Postoperative Care / Q000295:instrumentation*; D013059:Spectrum Analysis, Raman / Q000295:instrumentation*; D013997:Time Factors; D014545:Urinary Calculi / Q000737:chemistry*
keywords: CCD; IR; Raman; SVM; charge-coupled device; infrared; nephrolithiasis; spectrum analysis; support vector machine; urinary calculi; urolithiasis