Understanding the Popcorn Effect During Holmium Laser Lithotripsy for Dusting

Area of Science:

• Urology
• Endourology
• Laser Lithotripsy

Background:

• Ureteroscopic stone dusting aims to fragment calculi into particles less than 1 mm.
• The popcorn technique is an in vitro method for stone fragmentation.
• Optimizing laser settings and fiber proximity is crucial for efficient dusting.

Purpose of the Study:

• To evaluate the impact of low and high power settings on the popcorn technique.
• To determine the relationship between laser fiber-to-stone distance and calyceal size on submillimeter fragmentation.
• To guide strategies for improving ureteroscopic dusting techniques.

Main Methods:

• BegoStones of two sizes (127 mm³ and 411 mm³) were used to simulate renal calyces.
• A 120 W Holmium:YAG laser with a 242 μm fiber was employed.
• Fiber tip distances of 0 mm and 2 mm, and various power settings (20 W and 40 W) with different frequencies and pulse modes were tested.

Main Results:

• Direct fiber contact with the stone produced significantly more submillimeter fragments than a 2 mm distance (P < .05).
• Higher frequencies, regardless of pulse energy, increased submillimeter fragment distribution.
• The technique was more effective in the smaller calyceal model at a 2 mm distance, with short pulse superior to long pulse.

Conclusions:

• The popcorn technique is most effective with direct fiber-to-stone contact and in smaller calyceal models.
• Employing higher frequencies during laser lithotripsy may enhance dusting outcomes.
• These findings can inform optimization of ureteroscopic dusting procedures.