SuperPulsed thulium fiber laser shows several advantages

U.S. academic centers using the Soltive SuperPulsed Laser System to treat stones are finding it offers several advantages compared with holmium:YAG laser lithotripsy. But more research comparing the two is needed, according to a presentation at the 2019 World Congress of Endourology in Abu Dhabi, United Arab Emirates.

The Soltive SuperPulsed Laser System is a new lithotripsy platform. It is different than holmium:YAG laser technology, which urologists have used for more than 20 years to treat kidney stones, according to presenting author Wilson Molina, MD, professor of urology and director of the Kidney Stone Disease Program at the University of Kansas Medical Center, Kansas City.

Whereas holmium:YAG laser lithotripsy typically uses 200-μm to 365-μm optical laser fibers, the Soltive SuperPulsed Laser System allows the use of 150-μm core-sized fibers. Dr. Molina, along with urologist colleagues from Ohio State University, Columbus, presented a comparison of lithotripsy with a 242-μm core-sized fiber holmium:YAG (AccuMax 200), to the 150-μm core-sized SPTF.

“The thulium fiber platform has an advantage compared to the holmium:YAG in that it’s a portable system, which urologists can plug into a 120-volt outlet. If you can plug in your cell phone, you can plug in the machine,” Dr. Molina said.

Another advantage of the new technology, which the FDA cleared in August 2019, is that it isn’t noisy, according to Dr. Molina.

The Soltive SuperPulsed Laser System offers laser settings that the holmium does not, including high-frequency settings up to 2400 Hz. Urologists could use the Soltive SuperPulsed Laser System for dusting or fragmenting kidney stones, Dr. Molina said.

Soltive laser energy highly absorbed by water

In theory, the Soltive technology should be more effective for stone treatment because the laser's energy is highly absorbed by water.

“The laser energy is emitted at a wavelength of 1,940 nm, which is at the tip of the curve for water absorption. For that reason, it is probably more effective than the holmium laser,” he said.

Because the profile of the beam generated by the Soltive SuperPulsed Laser System is smaller than the beam profile created by the holmium laser, the Soltive SuperPulsed Laser System can use smaller laser fibers-as low as 50 μm, based on bench testing. The holmium laser can only use fibers greater than 200 μm.

“There are three advantages of using smaller fibers. Number one, smaller fibers allow the ureteroscopes to have a better flexion in order to navigate inside the kidney easier. The Olympus 150 µm fiber has greater flexibility and is able to bend to a tighter diameter before thermal breakdown compared to the AccuMax 200. Number two, with small fibers, we have better irrigation during the procedure with better visualization. Third, it potentially delivers energy in a smaller area of the stone, creating fragments that are smaller dust-type fragments,” Dr. Molina said.

Nearly all patients with kidney stones who can be treated with an endoscopic retrograde approach would benefit from the new technology.

“I think this laser could be used for a retrograde approach in patients that have larger stones that cannot undergo the percutaneous approach for reasons such as other comorbidities because it has the potential to be faster in terms of breaking up the stones,” Dr. Molina said.

The drawback to using the Soltive SuperPulsed Laser System is that it's new and has had limited use in a clinical setting, though more data will soon be available through a limited launch of the technology initiated in October 2019 at a total of 15 sites.

“There is some long-term clinical data from a similar technology abroad that is promising. But until we have long-term clinical data that compares with the holmium laser, we cannot make any consistent evaluation,” Dr. Molina said.

Dr. Molina and colleagues have submitted an abstract of the first 25 cases detailing use of the laser to perform the retrograde approach, but it is not yet published. He said researchers have shown so far that the thulium laser is feasible to use and is safe for patients.

Dr. Molina helped to develop the Soltive SuperPulsed Laser System and is a consultant for Olympus.