Pre-clinical evaluation of a laser system with emission control based on stone vs soft tissue recognition

To evaluate the feasibility and performance of the StoneSense™ module (SSM; IPG Medical, Marlborough, MA, USA), a prototype real-time target recognition unit integrated into a IPG Thulium Fiber Laser (TFL).

The SSM analyses the spectral signature of back reflected light-emitting diode (LED) light from the target, stopping laser energy emission when incoming signal is originating from tissue or when the fibre-to-target distance is larger than pre-defined threshold (typically, ≥2-4 mm). The ex vivo tests were conducted on artificial BegoStone phantoms ((Bego GmbH & Co. KG, Bremen, Germany) embedded in porcine kidney tissue using energy settings of 0.1-2 J and 5-100 Hz at two fibre-scanning speeds (1 and 3 mm/s) through a translation stage movement. Human urinary stones were subsequently tested at 2 and 5 mm/s with setting of 0.5 J × 20 Hz. The in vivo trial was conducted by lithotripsy of pre-implanted human stones in porcine urinary tract. Primary outcome measures included ablation efficiency as well as specificity and sensitivity of stone recognition.

Soft tissue ablation was completely prevented in all the ex vivo trials while maintaining high lithotripsy efficiency. Mean stone ablation reduction was 2.75% and 3% at fibre scanning speeds of 1 and 3 mm/s, respectively. The system achieved 100% sensitivity and up to 98% specificity in inhibiting laser emission to soft tissue. In vivo, complete dusting with fragments <500 μm was achieved for all studied stone types without observable mucosal injury. Specificity ranged from 85% to 100%, while sensitivity ranged from 90% to 100%.

Integration of back reflected-light-spectra-based laser emission control into a TFL-based lithotripsy system is feasible and effective. The SSM enables precise real-time stone recognition, minimises unnecessary lasing, and preserves dusting efficiency.