Fig. 2.8. Schematic absorption spectrum of hemoglobin (Hb), Oxyhemoglobin (Hbo2) and melanin (Me) to show absorption peak of Hb at 755 nm (courtesy of Cynosure Lasers)
achieved with 20 J/cm2 and double pulses. These parameters produced almost a two-thirds reduction in vessels 0.4-1 mm in diameter after three treatments. Small vessels respond poorly if at all. Others have treated leg veins measuring 0.3-2 mm in diameter in patients with Fitzpatrick skin types I-III with a 3-ms-pulsed alexandrite laser, 8-mm spot, fluences of 6080 J/cm2, and associated dynamic epidermal cryogen cooling. Four weeks after a single treatment, 48 sites were evaluated; 35% of the treated sites had cleared by more than 75 %, another 33 % had cleared by more than 50%. By 12 weeks 65% of treated areas showed greater than 75% clearance. Hyperpigmentation was seen in 35% of treated areas and treatment was noted to be uncomfortable.
Diode lasers were originally introduced in the 1980s with power outputs of only 100 mW. Multiple diode laser arrays have now been developed which can be coupled directly into fiber optic delivery devices. Laser outputs have now increased to 60 W or more. Diode lasers can emit light over a broad range of wavelengths from 600 to 1020 nm. Most medical research has been with diode lasers such as galliumarsenide (GaAs) and gallium-aluminum-arsenide (GaAlAs) emitting light in this 795- to 830-nm range.
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