Seek and destroy: A novel laser system with real-time automatic target identification for urinary stone lithotripsy. An in-vivo study

Introduction & Objectives: Thermal injuries related to Holmium laser based lithotripsy of the upper urinary tract are an underestimated and challenging problem in stone therapy. Currently, surgical precision solely relies on visual recognition when applying laser energy for stone disintegration. We developed a novel laser system using real-time spectral information for feedback control blocking the therapeutic laser beam, when no stone fragment is targeted. Materials & Methods: Ureteric and intrarenal Holmium laser lithotripsy inside urinary tracts of two domestic pigs was performed by an experienced endourology surgeon in-vivo. Human stone fragments (4-6 mm) were placed in both ureters, renal pelvis and bladder. In a standardized test series, laser lithotripsy was executed with and without the novel fluorescence feedback system in separate trial runs. Full disintegration of stones was performed with a pulse rate of 20 Herz and 0.5 Joule. After nephroureterectomy and cycstectomy, the urinary tract specimens were examined for laser induced lesions by a pathologist. Results: Using both setups sufficient disintegration of the human stone samples was achieved. Upon macroscopic and microscopic examination numerous superficial and deep thermal lesions were noted in the ureter and renal pelvis after lithotripsy utilizing a commercial Holmium laser system, while no such damage was found in the specimen after treatment using the novel system. In both test runs no thermal lesions were observed in the bladder. There was no evidence of organ perforation. Conclusions: Our study provides proof-of-concept for a novel laser system with automatic target identification in real time for laser lithotripsy. We believe that this concept will provide significant improvement in patient safety and surgical precision in stone therapy. Further studies and evaluation in humans are however needed to confirm this hypothesis.