Presently the three types of Q-switched lasers, the QSRL, QSAL and QSYL, are considered the definitive treatment method for tattoos and dermal melanocytosis and as for the treatment of regular nevus of Ota and acquired dermal melanocytosis, complete clearance is expected within a number of treatments. In Asian countries where dermal melanocytosis such as nevus of Ota are prevalent, the efficacy of lasers for not only dermal melanocytosis but also for epidermal lesions such as solar lentigines, secured the role of lasers as the king of treatment for benign cutaneous pigmented lesions 5). These lasers spread throughout the world quickly and the efficacy of laser tattoo removal became a proven fact. Prior to this period, lasers were thought to be capable of treating lesions limited to the skin surface and it came as a surprise to everyone that lasers were in fact capable of selectively destroying intra-dermal pigments such as tattoo pigments. The establishment and limitations of nano-second Q switched lasers: During the period from 1990 to 1994, the clinical application of these lasers came in succession and their efficacies were reported 2– 4). The clinical application of these 3 types of PLs secured the position of lasers in the field of dermatologic surgery. These made it possible for near permanent epilation through selective destruction of hair follicles. Thirdly are the various long-pulsed hair removal lasers, such as the alexandrite (755 nm), diode (810/940 nm) and Nd:YAG (1064 nm) used at pulse durations ranging from 2∼100 msec. The ns-domain Q-switched ruby laser (QSRL/694 nm, 20 ns), the Q-switched alexandrite laser (QSAL/755 nm, 50 ns) and the Q-switched Nd:YAG laser (QSYL/1064 nm, 5∼10 ns) are 3 PLs that made the treatment of tattoos and difficult dermal melanocytic lesions such as nevus of Ota, possible. Secondly are the nanosecond Q-switched lasers (ns-lasers) selectively targeting pigmented lesions including tattoo pigments and dermal melanocytosis. The wavelength in the vicinity of 590 nm and a pulse duration of 0.5∼3 ms, made possible the treatment of port-wine stains and telangiectasia. Firstly is the pulsed dye laser which targets the hemoglobin in dermal capillaries. The laser energy must be at a wavelength which is highly absorbed by the target relative to the surrounding normal tissue and 2: The pulse duration used must be shorter than the time it takes for heat to escape through conduction.īased on this theory, three types of laser have been realized which enabled dramatic improvements in clinical results in the treatment of pigmented targets. According to the theory of selective photothermolysis proposed by Anderson and Parrish, two conditions are required to selectively destroy a target: 1). However, if a selective destruction of a certain structure were the purpose, the use of a PL would be advantageous. If the purpose of the treatment is to vaporize or ablate living tissue from the surface of the target, the distinction between the two could be small. One is continuous wave lasers (CWL), and the other is the pulsed laser (PL). The history of the evolution of short pulsed lasers: For the treatment of cutaneous pigmented lesions, two types of laser emission mode may be used. The background behind the appearance of picosecond lasers
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