Prediction of intraoperative energy consumption during thulium fiber laser lithotripsy using stone volume and density

Urinary stone disease is a global health concern where surgical planning often relies on surgeon experience. This study aims to quantify the relationship between stone characteristics and total Thulium Fiber Laser (TFL) energy consumption and to derive a predictive energy coefficient to optimize operative efficiency. This prospective, observational clinical trial included 61 patients undergoing ureterorenoscopy or retrograde intrarenal surgery between June 2025 and January 2026. Preoperative stone volume (V) and density (Hounsfield Units, HU) were measured using non-contrast CT. Intraoperative parameters, including total energy (Joules) and ablation time, were recorded. A Specific Energy Coefficient (Jx10 3 /mm 3 xHU) was calculated, and a multiple linear regression model validated via bootstrapping (1000 resamples) was developed to predict energy requirements. The median stone volume was 417.50 mm 3 , and the mean density was 944.21 HU. The median total energy used was 22,079 J. The median Specific Energy Coefficient, scaled for practical clinical utility, was 48.13 Jx10 3 /mm 3 xHU. A very strong positive correlation was found between stone volume and total energy (rho = 0.961, p < 0.001). The regression model (E = -1190.917 + 39.694 x V + 0.666 x D) demonstrated excellent predictive power (Adjusted R 2 = 0.934). Bootstrapping validation confirmed the stability of the predictors, identifying stone volume as the primary independent driver. Thulium Fiber Laser lithotripsy demonstrates promising preliminary predictability driven primarily by preoperative stone volume. The developed model serves as a preliminary framework for forecasting energy requirements using CT parameters; however, multi-center studies with larger independent validation cohorts are strictly required before widespread clinical application.