Evaluation of StoneSense™ automatic target recognition in thulium fibre laser lithotripsy: a multi-model in vitro study

To determine the maximal stone-to-fibre firing distance permitted by StoneSense™ (IPG Medical, Marlborough, MA, USA) automatic target recognition (ATR) integrated into a thulium fibre laser (TFL) system, and to evaluate its effects on ablation efficiency, energy delivery, and thermal dispersion in complementary in vitro models.

An IPG Medical TFL prototype with integrated ATR was evaluated using BegoStone (Bego GmbH & Co. KG, Bremen, Germany) phantoms in three experimental settings. First, maximal ATR-permitted firing distance was determined using a stabilised Z-stage under varying light-emitting diode (LED) intensities (50% vs 100%) and laser frequencies (1 J, 10 Hz vs 20 Hz). Second, in a cuvette-mesh model with continuous irrigation and thermocouple monitoring, lithotripsy was performed with ATR activated and inactivated to assess active laser time, energy delivery, ablation efficiency, procedural duration, and temperature change. Third, a single-surgeon simulated retrograde intrarenal surgery (RIRS) model evaluated fragmentation over 120 s of laser emission.

The ATR restricted laser firing to a narrow stone-to-fibre distance of approximately 2.3-2.7 mm, with no statistically significant differences observed between the tested LED intensities or pulse frequencies. In the cuvette model, ATR activation reduced active laser time (mean [SD] 146 [18] vs 179 [19] s; P = 0.020) and energy delivery (mean [SD] 1.46 [0.18] vs 1.79 [0.20] kJ; P = 0.021), improved ablation efficiency (mean [SD] 1.77 [0.25] vs 1.42 [0.13] mg/J; P = 0.022), and reduced thermal rise (mean [SD] 4.2 [0.3] vs 5.1 [0.5]°C; P = 0.001), with a modest increase in total procedure time. In the simulated RIRS model, ATR increased ablated mass and efficiency (P < 0.05), with longer procedural duration.

The StoneSense ATR constrains TFL activation to a defined optical range and improves ablation efficiency while reducing energy waste and thermal rise in vitro. Although associated with increased procedural duration, ATR-guided lithotripsy may enhance precision and thermal safety.