Abstract: This study investigates the threshold radiant exposures required to irreversibly damage cutaneous blood vessels using a pulsed dye laser (PDL) operating at 585 nm. Evaluation of blood vessel damage and blood flow stoppage was achieved using Doppler imaging in a color Doppler optical coherence tomographic (CDOCT) system. Hamster dorsal skin flap window vessels were irradiated with radiant exposures ranging from 2.5 - 8 J/cm$+2$/. A 5 mm spot size and 360 microsecond pulse duration were used. Irradiation sites were imaged with CDOCT prior to, immediately after, and a minimum of 24 hours after delivery of laser energy. Magnitude and color Doppler images provided information such as approximate vessel size, depth, and changes in blood flow velocity. Vessel stenosis, temporary occlusion, permanent occlusion, hemorrhaging, and changes in flow velocity were frequent results of laser irradiation visualized with CDOCT and video imaging. Probit analysis was used to estimate the 50% probability that a blood vessel of given size and type will be destroyed by a given radiant exposure. In most instances, arterioles required higher radiant exposures to be irreversibly damaged than venules of the same size. However, arteriole/venule pairs required approximately the same radiant exposures for visible damage to occur. Vessels of larger diameter required higher radiant exposures to coagulate than vessels of smaller diameter. !10
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