Presentation Authors: Benjamin PRADERE*, Tours, France, Ivan Lucas, Steeve Doizy, Darine Abi Haidar, Michel Daudon, Olivier Traxer, Paris, France
Introduction: Diagnostic of urolithiasis composition is the keystone for prophylactic treatment of stone disease. To date, the gold standard for stone composition analysis remains the infrared spectroscopy (IRS) with morphological study, that should be performed in all first-time formers. The objective of our study was to assess the feasibility of Raman spectroscopy (RS) in biological environments for stone composition analysis and to develop a laser fiber for intraoperative diagnosis.
Methods: A set of stones (>1000) were analyzed by the gold standard technique. The purest (>85% of same composition) were selected to be analyzed on a specific RS setup. We used a laser with a 785nm wavelength. A first analysis was performed in the air to obtain the spectral characteristics of each stone. Then an analysis in urinary environment was performed. Different urinary dilutions were tested to obtain the minimum concentration of proteins for interpretable spectra. A RS analysis with a specific small caliber fiber was then performed and the evaluation of the best settings for a potential peroperative use was done.
Results: Seven different classes of stones were analyzed: weddellite, whewellite, struvite, brushite, carbapatite, cystine and uric acid. A specific spectral signature was obtained in the air for each class of stones. A RS was performed in urine at different dilution, we were able to obtain the same spectral signature than in the air but with less intensity. In urine diluted, the intensity of the signal was stronger than in urine concentrated. Brushite stones has the worst signal in RS compared to the other one, presence of blood clots or proteins reduced the intensity and increased background noise. Our specific setup with laser fiber was able to give all the specific spectral signature for each stone in the air or in the urine.The distance between the laser and the stone impacted the intensity: the signal was maximum when the fiber was in contact of the stone. All the signals were obtained in less than 20 seconds.
Conclusions: Raman spectroscopy analysis of stone composition in urine is feasible and reproducible with a 785nm laser. We identified the best settings for a good analysis (urine diluted, fiber in contact...) and we were able to perform the analysis in less than 20 seconds. These results show the potential applicability of RS for a clinical endoscopic use in order to diagnose peroperatively the stone composition and adapt laser settings for the destruction of the stone.