LBA01-16: Comparative Analyses and Ablation Efficacy of Thulium Fiber Laser by Stone Composition

Sunday, April 30, 2023

7:00 AM – 9:00 AM CST

Location: S505

Poster Presenter(s)

Jeffrey Pace Johnson, MD

Weill Cornell Urology

Introduction: There is limited data on the ablation settings and photothermal effects of thulium fiber laser (TFL) lithotripsy across various stone compositions. We aim to identify settings by stone type that optimize efficiency and avoid undesirable effects (i.e. charring) during TFL lithotripsy.

Methods: Specimens of calcium oxalate monohydrate, calcium oxalate dihydrate, uric acid, struvite, cystine, carbonate apatite and brushite stones were ablated to =1mm residual fragments using 13 settings with the Coloplast© TFL Drive. Pre-ablation mass, post-ablation mass, ablation time and total energy were recorded. Samples were analyzed using FTIR spectroscopy and electron microscopy.

Results: Pulse duration impacted ablation effectiveness greatly with 75% of inadequate ablations occurring in medium or long pulse settings. Calcium oxalate dihydrate, cystine, and struvite ablated most efficiently with 0.2J x 100Hz, short pulse. Calcium oxalate monohydrate ablated most efficiently with 0.4J x 40Hz, short pulse. The average percent of mass lost during ablation was 57%; cystine averaged the highest at 71%. Charring was seen in 40% of stones, mostly in uric acid, cystine, and brushite stones. Electron microscopy of char demonstrated a porous melting effect. FTIR spectroscopy of brushite char demonstrated a chemical composition change to amorphous calcium phosphate.

Conclusions: Our trial is the first in vitro trial on stone ablation efficacy by stone composition. Across all settings and stone types 0.05J x 1000Hz was the most effective ablation setting, however this is above our clinically recommended power of <=20 W. When operating in the kidney and using clinically acceptable TFL settings to minimize the risk of thermal injury, we recommend starting with short pulse 0.2J x 100Hz and 0.4J x 40Hz to cover most stone types, and adjusting the settings based on visual ablation effects intraoperatively and the clinical scenario (e.g. limited irrigation flow, narrow infundibulum). Further investigation is needed to continue to optimize TFL stone treatment settings. SOURCE OF

Funding: Coloplast