In vivo results using photothermal tomography for imaging cutaneous blood vessels

Abstract

Previous studies suggest that optimal port wine stain (PWS) laser treatment parameters require knowledge of skin characteristics such as blood vessel size, depth, and distribution. Effective and rapid imaging modalities are not widely available. In the present study, photothermal tomography (PTT) images of an in vivo hamster window model and human PWS skin were obtained and analyzed. Subtherapeutic laser light pulses at 585 and 600 nm were applied to skin surface and image sequences acquired with an infrared camera. A nonnegatively constrained conjugate gradient algorithm was used to reconstruct a PTT image of the initial temperature distribution immediately following pulsed laser irradiation. Vessel dimensions determined from PTT images of hamster window model skin compared well with those measured directly using video microscopy. PTT images of human PWS skin contained vessels with estimated diameters of 200-250 jim over a 250-320 jtm depth range. Use of dual wavelength excitation (DWE) analysis allowed for imaging of shallow vessels.

Selection of optimal infrared detector for pulsed photothermal profiling of vascular lesions

“…This approach was developed further and studied by Milner et al 8,9 and others, 10,11,12 up to the point of demonstrating three-dimensional imaging of subsurface vasculature by utilizing a fast IR camera. 13,14,15 PWS are subsurface hypervascular lesions, located within the most superficial millimeter of human skin. Blood vessel size and depth distribution in PWS varies widely from patient to patient, with the highest fractional blood content on average 0.2−0.4 mm below the epidermal-dermal junction.…”