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[Results of the first multicenter study assessing the efficiency of a tissue sensor during thulium fiber laser
G Martov A1,2,3,4,5,6, S Andronov A1,2,3,4,5,6, M Adilkhanov M1,2,3,4,5,6
1Urological Center of the Central Clinical Hospital of Civil Aviation, Moscow, Russia.
Introduction:
Currently, the main surgical approach for urinary stone removal is minimally invasive endoscopic procedures. Various laser systems compatible with most modern instruments are used for stone disintegration. Due to high efficacy and minimal fragment retropulsion during fragmentation, the domestic thulium fiber laser has become a serious alternative to the conventional holmium laser. At the same time, the safety profile of thulium fiber lithotripsy remains debatable because of the potential risk of irrigation fluid heating and damage to surrounding tissues during fragmentation. Implementation of a "Tissue Sensor" (TS) capable of differentiating stone from mucosa during lithotripsy allows automatic cessation of laser emission to prevent injury to the organ wall.
Aim:
To assess efficiency and improve the safety of lithotripsy using a new-generation thulium fiber laser with the tissue sensor function activated.
Materials And Methods:
The study included 70 patients from three medical centers aged 25 to 73 years with 101 ureteral and renal stones. Ureteroscopy with laser lithotripsy was performed in 23 patients, retrograde intrarenal surgery in 30, and percutaneous nephrolithotomy in 17. Mean stone volume was 0,7+/-0,4 cm3; stone density was 1080+/-370 HU. Various thulium fiber laser (TFL) settings were used for stone disintegration (dusting, fragmentation, popcorning). In addition to the standard rectangular pulse (Standard), different types of pulse modulation were used: minimal retropulsion modes (MRP); fine dusting (FinePulse); and fragmentation as a "packet" of pulses (UltraPulse). Energy and frequency ranges were 0,2-1,5 J and 5-40 Hz, respectively, for Standard, MRP, and FinePulse. For UltraPulse energies of 3-30 J and frequencies of 1-4 Hz were used. In all patients, laser lithotripsy was performed with the "Tissue Sensor" function enabled. Safety, based on the nature of mucosal impact in the organ where fragmentation was performed, was assessed using the Traxer-Sierra scale from 0 to 5. Early postoperative complications were recorded and graded using the modified Clavien-Dindo classification.
Results:
The mean operative time was 48+/-28 minutes; laser time 16+/-13 minutes; pedal time 7 +/- 6 minutes; laser emission time 5+/-4 minutes. The TS efficiency coefficient, defined as the ratio of emission time to pedal time, was 65%, reflecting frequent sensor activation to prevent injury to surrounding tissues. The complete stone clearance rate was 98%. In the vast majority of cases (96%), no complications were observed. According to questionnaires, operating urologists reported that TS function did not affect procedure duration while helping avoid soft-tissue injury in most cases. No severe thermal injuries on the Traxer-Sierra scale were recorded (no injury in 46% of cases; grade I injury in 47%).
Conclusion:
A tissue type recognition system (Tissue Sensor) improves the safety of lithotripsy by reducing unintended mucosal injury and preventing an increase in irrigation fluid temperature while maintaining high stone disintegration efficacy.