V03-03: Targeting Microbubble Enhancement of Holmium Laser Stone Ablation
Holmium laser lithotripsy is the most common method of stone fragmentation during the ureteroscopic management of calculi in the United States. The laser achieves the therapeutic effect of stone fragmentation through multiple mechanisms, including a photothermic effect and the generation of cavitation bubbles and shockwaves at the interface of urine/fluid and the stone. We hypothesized that lipid-shell microbubbles with stone-binding properties could enhance stone fragmentation in holmium laser lithotripsy through enhancement of cavitation effects.
Synthetic hydroxyapatite pellets and a pulsed holmium:YAG laser were used for the studies. Targeting microbubbles were acquired from a clinical trial-stage insonation-based stone treatment product. The microbubbles are a lipid-shell perfluoroalkane gas configuration with calcium-binding moieties incorporated into the shell to facilitate stone targeting. The laser settings were 0.2 Joules at 10 Hertz for 30 pulses per cycle. A high-speed Shimadzu Hyper Vision HPV-X2 camera (Shimadzu, Kyoto, Japan) was used to capture still and video images of the action of the targeting microbubbles and other pressure effects around the stone during laser pulsing. Pellets were weighed before and after each of 6 cycles, and ablation in the microbubble-inclusive runs was compared to a no-targeting-microbubble control with a two-tailed t-test.
Holmium laser ablation resulted in a mean loss of 6.0 ± .81 mg of hydroxyapatite per 30 pulse cycle at 0.2 Joules without targeting microbubles and 10.2 ± .98 mg per cycle with targeting microbubbles with a p value of
Targeting microbubbles appear to increase the per-cycle volume of ablated stone by holmium:YAG laser energy by 70%. Targeting microbubbles could improve the lithotripsy phase of endoscopic stone procedures resulting in decreased operative time, higher stone-free rates, and thereby improved patient outcomes during holmium laser lithotripsy.
Funding: This study was funded by Applaud Medical.