Comparison of p-Tm:YAG, TFL and Ho:YAG's in vitro ablation rates on synthetic and human stones

Objective: To compare in vitro the ablation rates of p-Tm:YAG, TFL and Ho:YAG against synthetic and human stones. Material and methods: p-Tm:YAG, TFL and Low-Power (LP) Ho:YAG were compared using 270 μm core-diameter laser fibres (CDF); experiments with 200 μm(p-Tm:YAG) and 150 μm-CDF (TFL) were also included. A continuous laser emission was applied through a spiral trajectory for 20 seconds with the laser fibre tip in contact with synthetic hard (HSP) and soft stone phantoms (SSP) submerged in saline. "Dusting" settings for p-Tm:YAG(0,6 J-20 Hz-Flex Long Pulse), TFL(0,5 J-30 Hz-Short Pulse) and Ho:YAG(0,5 J-30 Hz-Long Pulse) and "Fragmentation" settings for p-Tm:YAG(1 J-15 Hz-Captive), TFL(1 J-15 Hz-Short Pulse) and Ho:YAG(1 J-15 Hz-Long Pulse) were analysed. Then, experiments for human calcium oxalate monohydrate (COM), uric acid (UA) and cystine (CYS) stones were performed with single laser pulses at 0.6 J, 0.8 J and 1.0 J for p-Tm:YAG (Captive Fragmenting mode), TFL (Short Pulse) and Ho:YAG (Long Pulse). Synthetic and human stone samples were dried before three-dimensional scanning to measure ablation rates (ARs) and ablation volume per pulse (AVP). Results: For synthetic stones with 270 μm-CDF, the p-Tm:YAG and TFL presented similar ARs, except in Fragmentation against HSP (95,1 ± 13,6vs67 ± 14 p = 0,02, respectively). Both p-Tm:YAG and TFL achieved higher ARs than Ho:YAG in all settings. p-Tm:YAG-200 μm-CDF and TFL-150 μm-CDF presented similar ARs, except in Fragmentation against HSP(78,4 ± 8vs42,5 ± 2,6 mm/min,p = 0,0002). Both p-Tm:YAG-200 μm-CDF and TFL-150 μm-CDF presented at least 50% higher ARs than 270 μm-Ho:YAG. For human stones with COM, TFL exhibited higher AVP compared to p-Tm:YAG and Ho:YAG across all pulse energies (258,2 ± 213vs81,7 ± 31,9vs41,5 ± 25,4 μm p = 0,01, respectively). Against UA, Ho:YAG demonstrated higher AVP compared to TFL and p-Tm:YAG (355,2 ± 161vs99,8 ± 76,7vs292,9 ± 203,1 μm p = 0,0005, respectively). For CYS, Ho:YAG presented higher AVP but without significance (99,8 ± 76,7 vs 49,3 ± 36,3 vs 38,8 ± 12,2 μm, p = 0,09). Conclusion: p-Tm:YAG and TFL achieved higher ARs than LP-Ho:YAG against synthetic stones in vitro. For human stones, TFL achieved the highest AVP against COM while LP-Ho:YAG delivered higher AVPs against UA and CYS, for which TFL performed worst.