Pushing Back: A Comparative Analysis of the Retropulsive Forces Generated by Modern Laser Systems Using an In Vitro Model of Laser Lithotripsy "Presentation" - Aymon Ali
April 28, 2025
Aymon Ali compares three laser systems and discusses how the MOSES system generates the least stone retropulsion during lithotripsy. These findings provide valuable comparative data on how different laser technologies address the significant challenge of stone movement during procedures, though Dr. Ali notes that testing with actual human stones will be necessary to fully assess clinical implications.
Biography:
Aymon Ali, MD, Department of Urology, University of California, Irvine, Irvine, CA
Aymon Ali, MD, Department of Urology, University of California, Irvine, Irvine, CA
Read the Full Video Transcript
Aymon Ali: Dear viewers, my name is Aymon Ali, one of the Endourology fellows here at the University of California, Irvine. Today, I will be talking about my project, titled "Pushing Back, A Comparative Analysis of the Repulsive Forces Generated by Modern Laser Systems Using an In Vitro model of Laser Lithotripsy."
Retropulsion of calculi poses a significant barrier to efficient laser lithotripsy. Traditional laser systems, typically Holmium:YAG lasers, generate and collapse an asymmetrical vapor bubble, which results in retropulsion. Novel laser systems, including thulium fiber lasers, deliver lower peak power and pulse width, which are purported to decrease retropulsion.
We investigated the retropulsive effects of three common laser systems in in vitro ureteric model. This consisted of the MOSES laser, thulium laser, and SOLTIVE laser systems. In summary, our methods included assembling a large water bath of 30 liters volume, containing 15 liters of sterile water at 37 degrees centigrade. A polymer tube, 30 centimeters in length, 12 millimeters in outer diameter, and with one centimeter graduations, was secured to the base of the tub. A 4 millimeter ceramic ball was placed within the tube, simulating a calculus.
Each laser system was fired with a 200 micron fiber centrally at the ceramic ball, approximately 1 millimeter away from the ball surface. Two different setting types were utilized-- a dusting setting at 0.3 joules and 50 Hertz, and a fragmentation setting at 1 joule and 15 hertz. A Holmium:YAG laser with the MOSES setting turned off was used as a control. The total distance traveled in 30 seconds was recorded in centimeters in decuplicate.
Our results demonstrated that using both dusting and fragmentation settings, MOSES with the MOSES mode on, demonstrated the lowest retropulsion at 2.55 centimeters and 3.40 centimeters, respectively. This was not significantly different with the MOSES setting turned off. The SOLTIVE laser system using the dusting settings demonstrated the third lowest retropulsion at 8.07 centimeters. This was non-inferior to the MOSES system with the MOSES setting off.
However, using fragmentation settings, this demonstrated the highest retropulsion compared to the MOSES laser system with the MOSES setting off. The thulium laser demonstrated the highest degree of retropulsion, using dusting settings at 11.75 centimeters, and the second highest using fragmentation settings at 9.73 centimeters. Both of these results were significantly higher than the MOSES laser system with the MOSES setting off.
In conclusion, in an in vitro model of stone retropulsion, MOSES with the MOSES setting on and off, demonstrated the lowest overall retropulsion using dusting and fragmentation settings. This was followed by the SOLTIVE system, and finally, the thulium system, respectively. Further testing is warranted using ex vivo or in vivo human calculi to assess the reproducibility of these results in the context of stone fragmentation. Thank you.
Aymon Ali: Dear viewers, my name is Aymon Ali, one of the Endourology fellows here at the University of California, Irvine. Today, I will be talking about my project, titled "Pushing Back, A Comparative Analysis of the Repulsive Forces Generated by Modern Laser Systems Using an In Vitro model of Laser Lithotripsy."
Retropulsion of calculi poses a significant barrier to efficient laser lithotripsy. Traditional laser systems, typically Holmium:YAG lasers, generate and collapse an asymmetrical vapor bubble, which results in retropulsion. Novel laser systems, including thulium fiber lasers, deliver lower peak power and pulse width, which are purported to decrease retropulsion.
We investigated the retropulsive effects of three common laser systems in in vitro ureteric model. This consisted of the MOSES laser, thulium laser, and SOLTIVE laser systems. In summary, our methods included assembling a large water bath of 30 liters volume, containing 15 liters of sterile water at 37 degrees centigrade. A polymer tube, 30 centimeters in length, 12 millimeters in outer diameter, and with one centimeter graduations, was secured to the base of the tub. A 4 millimeter ceramic ball was placed within the tube, simulating a calculus.
Each laser system was fired with a 200 micron fiber centrally at the ceramic ball, approximately 1 millimeter away from the ball surface. Two different setting types were utilized-- a dusting setting at 0.3 joules and 50 Hertz, and a fragmentation setting at 1 joule and 15 hertz. A Holmium:YAG laser with the MOSES setting turned off was used as a control. The total distance traveled in 30 seconds was recorded in centimeters in decuplicate.
Our results demonstrated that using both dusting and fragmentation settings, MOSES with the MOSES mode on, demonstrated the lowest retropulsion at 2.55 centimeters and 3.40 centimeters, respectively. This was not significantly different with the MOSES setting turned off. The SOLTIVE laser system using the dusting settings demonstrated the third lowest retropulsion at 8.07 centimeters. This was non-inferior to the MOSES system with the MOSES setting off.
However, using fragmentation settings, this demonstrated the highest retropulsion compared to the MOSES laser system with the MOSES setting off. The thulium laser demonstrated the highest degree of retropulsion, using dusting settings at 11.75 centimeters, and the second highest using fragmentation settings at 9.73 centimeters. Both of these results were significantly higher than the MOSES laser system with the MOSES setting off.
In conclusion, in an in vitro model of stone retropulsion, MOSES with the MOSES setting on and off, demonstrated the lowest overall retropulsion using dusting and fragmentation settings. This was followed by the SOLTIVE system, and finally, the thulium system, respectively. Further testing is warranted using ex vivo or in vivo human calculi to assess the reproducibility of these results in the context of stone fragmentation. Thank you.