Arkadiusz Miernik1,2, Yvan Eilers3, Christoph Nuese3, Carsten Bolwien3, Armin Lambrecht3, Albrecht Hesse4, Jens J Rassweiler5, Daniel Schlager6, Konrad Wilhelm6, Ulrich Wetterauer6, Martin Schoenthaler6. 1. Department of Urology, University Medical Centre Freiburg, Hugstetterstr. 55, 79106, Freiburg, Germany. arkadiusz.miernik@uniklinik-freiburg.de. 2. Fraunhofer Institute for Physical Measurement Techniques, Heidenhofstraße 8, 79110, Freiburg, Germany. arkadiusz.miernik@uniklinik-freiburg.de. 3. Fraunhofer Institute for Physical Measurement Techniques, Heidenhofstraße 8, 79110, Freiburg, Germany. 4. German Urinary Stone Analysis Centre Bonn, Friedensplatz 16, 53111, Bonn, Germany. 5. SLK Kliniken Heilbronn, Department of Urology and Pediatric Urology, University of Heidelberg, Am Gesundbrunnen 20-26, 74078, Heilbronn, Germany. 6. Department of Urology, University Medical Centre Freiburg, Hugstetterstr. 55, 79106, Freiburg, Germany.
Abstract
PURPOSE: Raman spectroscopy allows immediate analysis of stone composition. In vivo stone analysis during endoscopic treatment may offer advantages concerning surgical strategy and metaphylaxis. Urinary stone components were evaluated utilizing an experimental setup of a Raman system coupled to commercial laser fibers. METHODS: Samples of paracetamol (acetaminophen) and human urinary stones with known Raman spectra were analyzed using an experimental Raman system coupled to common commercial lithotripsy laser fibers (200 and 940 µm). Two different excitation lasers were used at wavelengths of 532 and 785 nm. Numerical aperture of the fibers, proportion of reflected light reaching the CCD chip, and integration times were calculated. Mathematical signal correction was performed. RESULTS: Both the laser beam profile and the quality of light reflected by the specimens were impaired significantly when used with commercial fibers. Acquired spectra could no longer be assigned to a specific stone composition. Subsequent measurements revealed a strong intrinsic fluorescence of the fibers and poor light acquisition properties leading to a significant decrease in the Raman signal in comparison with a free-beam setup. This was true for both investigated fiber diameters and both wavelengths. Microscopic examination showed highly irregular fiber tip surfaces (both new and used fibers). CONCLUSIONS: Our results propose that laser excitation and light acquisition properties of commercial lithotripsy fibers impair detectable Raman signals significantly in a fiber-coupled setting. This study provides essential physical and technological information for the development of an advanced fiber-coupled system able to be used for immediate stone analysis during endoscopic stone therapy.
PURPOSE: Raman spectroscopy allows immediate analysis of stone composition. In vivo stone analysis during endoscopic treatment may offer advantages concerning surgical strategy and metaphylaxis. Urinary stone components were evaluated utilizing an experimental setup of a Raman system coupled to commercial laser fibers. METHODS: Samples of paracetamol (acetaminophen) and human urinary stones with known Raman spectra were analyzed using an experimental Raman system coupled to common commercial lithotripsy laser fibers (200 and 940 µm). Two different excitation lasers were used at wavelengths of 532 and 785 nm. Numerical aperture of the fibers, proportion of reflected light reaching the CCD chip, and integration times were calculated. Mathematical signal correction was performed. RESULTS: Both the laser beam profile and the quality of light reflected by the specimens were impaired significantly when used with commercial fibers. Acquired spectra could no longer be assigned to a specific stone composition. Subsequent measurements revealed a strong intrinsic fluorescence of the fibers and poor light acquisition properties leading to a significant decrease in the Raman signal in comparison with a free-beam setup. This was true for both investigated fiber diameters and both wavelengths. Microscopic examination showed highly irregular fiber tip surfaces (both new and used fibers). CONCLUSIONS: Our results propose that laser excitation and light acquisition properties of commercial lithotripsy fibers impair detectable Raman signals significantly in a fiber-coupled setting. This study provides essential physical and technological information for the development of an advanced fiber-coupled system able to be used for immediate stone analysis during endoscopic stone therapy.
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