Laser lithotripsy of a brushite crystalline aggregate stone model: fragment distribution vs. BegoStone and human stones.

Laser research is hampered by a lack of accurate stone models that replicate fragmentation during laser lithotripsy. We sought to assess the distribution of stone fragments from laser ablation of new brushite crystalline powder and brushite crystalline aggregate stone models and compare with human stones and BegoStone. Samples of 15:3 and 15:5 BegoStone, powder, and aggregate model stones were tested alongside human CHPD and COM stone samples. All samples were secured and hydrated before Ho: YAG laser energy was delivered (Lumenis P120H) using a 200-micron D/F/L fiber. Lithotripsy was performed by repeatedly translating the fiber automatically through a predetermined grid of points (MATLAB program) until > 50% of each sample was ablated. Fragments were separated by sieving. For each stone type, 70.2-96.9% of the mass of fragments consisted of particles smaller than 0.25 mm. The percentage by mass of fragments greater than 1 mm in trials with 0.8 J x 10 Hz settings was 0.5%, 0.0%, 1.1% and 5.1% for BegoStone 15:3, BegoStone 15:5, powder model, and aggregate model respectively, compared to 5.5% for CHPD and 16.2% for COM. Only the aggregate model, CHPD and COM samples produced fragments > 2 mm. The new aggregate model stone better replicates the fragment distribution of human stones after laser lithotripsy. The method of producing the aggregate model stone - incorporating crystal and chemical components found in urinary stones - holds promise for developing better stone models needed to address a range of important lithotripsy research questions.