• #6-2. Development of Medical Lasers in the 2010s




    In 2014, it was updated to 550ps and wavelength of 532nm. Considering the pulse duration of Q-switched alexandrite lasers is 60-70ns, PicoSure’s pulse duration is about hundred times shorter. This can increase the peak power by about 100 times which more effectively destroys tattoo ink particles than Q-switched alexandrite lasers and brings better therapeutic outcome.


    The Q-switched Nd:YAG laser has a pulse duration of 5-10ns. As for picosecond Nd:YAG laser, Syneron Candela’s PicoWay has the peak power of 400mJ and pulse duration of 450ps at wavelength of 1064nm, and 200mJ and 375ps at 532nm. Therefore, the pulse duration has not decreased drastically compared to the Q-switch mode (Table 2).


    Table 2. Comparison of picosecond lasers.


        The pulse duration of the Nd:YAG laser deserves our attention. Unlike the alexandrite laser, Nd:YAG laser has the pulse duration of 5-10ns with Q-switching. As shown in <Table 2>, the pulse duration of picosecond Nd:YAG laser is 2-10 times shorter compared to Q-switching and this is a drastic difference from PicoSure.


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    However, its peak power is not much higher than that of PicoSure. Considering the absorption coefficient of melanin as well as the output of Q-switched alexandrite and Q-switched Nd:YAG laser, the peak power of picosecond Nd:YAG laser should be about 20 times larger than that of PicoSure. However, in clinical practice, PicoSure and picosecond Nd:YAG laser are found to be similar in terms of therapeutic effect. In other words, a shorter pulse duration has lower risk of thermal damage, causes less pain and post-treatment side effects (burn, hypopigmentationm etc.) despite a low peak power.

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