Background and Objective: Successful laser treatment of port wine stain (PWS) birthmarks requires knowledge of lesion geometry. Laser parameters, such as pulse dura- tion, wavelength, and radiant exposure, and other treat- ment parameters, such as cryogen spurt duration, need to be optimized according to epidermal melanin content and lesion depth. We designed, constructed, and clinically tested a photoacoustic probe for PWS depth determination.
Study Design / Materials and Methods: Energy from a frequency-doubled, Nd:YAG laser (λ=532 nm, τp=4 nanoseconds) was coupled into two 1,500 mm optical ¨bers ¨tted into an acrylic handpiece containing a piezoelectric acoustic detector. Laser light induced photoacoustic waves in tissue phantoms and a patient's PWS. The photoacoustic propagation time was used to calculate the depth of the embedded absorbers and PWS lesion.
Results: Calculated chromophore depths in tissue phan- toms were within 10% of the actual depths of the phantoms. PWS depths were calculated as the sum of the epidermal thickness, determined by optical coherence tomography (OCT), and the epidermal-to-PWS thickness, determined photoacoustically. PWS depths were all in the range of 310±570 mm. The experimentally determined PWS depths were within 20% of those measured by optical Doppler tomography (ODT).
Conclusions: PWS lesion depth can be determined by a photoacoustic method that utilizes acoustic propagation time
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