Abstract: Because of the $GREQ 250 $mu@s pulsewidth emitted by the Ho:YAG laser used in clinical lithotripsy, it is unlikely that stress confinement occurs within the irradiated stones. Experimental data supports a thermal mechanism for Ho:YAG laser stone ablation. Previous work has shown that stone fragmentation occurs soon after the onset of the laser pulse, is uncorrelated to cavitation bubble formation or collapse, and is associated with low pressures. Moreover, lithotripsy proceeds fastest with desiccated stones in air (data based on laser ablation of calcium oxalate monohydrate stones), indicating that direct absorption of the laser radiation by the stone material is required for the most efficient ablation. Lowering the initial temperature of calculi reduces the stone mass-loss following 20 J of delivered laser energy: 2.2 $POM 1.1 mg vs 5.2 $POM 1.6 mg for calcium oxalate monohydrate (COM) stones ($MIN@80 vs 23$DGR@C), and 0.8 $POM 0.4 mg vs 2.2 $POM 1.1 mg for cystine stones ($MIN@80 vs 23$DGR@C), p $LSEQ 0.5. In all of the stone compositions examined, thermal breakdown products have been detected, e.g. CaCO$-3$/ from COM; free sulfur and cysteine from cystine; Ca$-2$/O$-7$/P$-2$/ from calcium hydrogen phosphate dihydrate, and cyanide and alloxan from uric acid. All of these observations are most consistent with a photothermal breakdown process induced by Ho:YAG laser lithotripsy.!22
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机译：摘要：由于临床碎石术中使用的Ho：YAG激光器发射的脉冲宽度为$ GREQ250μs，因此不太可能在受照射的结石内发生应力限制。实验数据支持了Ho：YAG激光石烧蚀的热机制。先前的工作表明，碎石碎裂在激光脉冲开始后不久发生，与空化气泡的形成或塌陷无关，并且与低压有关。此外，在空气中干燥的结石时碎石速度最快（基于草酸钙一水合物结石的激光烧蚀的数据），这表明，最有效的烧蚀需要石材直接吸收激光辐射。降低结石的初始温度可降低20 J传递的激光能量后的石材质量损失：2.2美元POM 1.1毫克vs. 5.2美元POM一水草酸钙（COM）石头1.6毫克（$ MIN @ 80 vs 23 $ DGR @ C ），以及胱氨酸结石的0.8 $ POM 0.4毫克vs.2.2 $ POM 1.1毫克（$ MIN @ 80 vs 23 $ DGR @ C），p $ LSEQ 0.5。在所有检查过的石材组合物中，都检测到了热分解产物，例如CaCO $ -3 $ /来自COM；从胱氨酸中释放出硫和半胱氨酸；来自磷酸氢钙二水合物的Ca $ -2 $ / O $ -7 $ / P $ -2 $ /和来自尿酸的氰化物和四氧嘧啶。所有这些观察结果与Ho：YAG激光碎石术引起的光热击穿过程最一致！22
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