Optical characterization of endoscopes for StoneSense™ compatibility

BACKGROUND AND OBJECTIVE: The StoneSense Module (SSM), integrated within IPG laser lithotripsy systems, uses endoscopic white-light illumination for real-time stone-tissue discrimination, enabling conditional laser firing only in the presence of a confirmed calculus. SSM performance depends on the endoscope's optical output falling within defined thresholds. We aimed to characterize commercially available flexible ureteroscopes and cystoscopes against predefined SSM compatibility criteria. METHODS: Twenty device-videobox combinations (15 flexible ureteroscopes, 4 cystoscopes, 1 semirigid ureteroscope; 7 manufacturers) with complete StoneSense-processed band data were included. Total power and spectral band power (Bands 1-3) were measured at three brightness levels in free-space configuration (no fiber inserted), and temporal profile was classified by oscilloscopy. Per-fiber band power was modeled from these free-space measurements, not measured with the fiber in the working channel. Predicted SSM band-power compatibility was assessed per device-brightness-fiber combination against predefined thresholds, with a minimum PWM frequency of 2 kHz as the temporal criterion. RESULTS: All 20 devices exhibited continuous-wave (CW) emission, conferring unconditional temporal SSM compatibility. Following recalibration of the SSM reference thresholds, the 200 µm and 365 µm fibers were predicted to meet SSM band power thresholds at medium/maximum brightness for 18 of the 20 devices, with the Karl Storz Flex XC and the Olympus CYF-VH cystoscope as the two exceptions at both fiber sizes. Additional saturation, restricted to the 550 µm and 940 µm fibers, was identified for six further devices (Table 1). Four Olympus platforms showed modeled sub-threshold power at minimum brightness. Four illumination archetypes were identified: blue-pump LED, red-shifted LED, Olympus intermediate LED, and LED-phosphor. CONCLUSIONS: The 200 µm and 365 µm fibers provide the broadest predicted compatibility (18/20 platforms), with the Flex XC and CYF-VH as the exceptions. Predicted incompatibilities are otherwise device-architecture-driven and manageable through fiber and brightness selection. A device-level compatibility reference matrix based on modeled estimates is provided.