Modeling laser treatment of port wine stains with a computer-reconstructed biopsy.

Abstract

BACKGROUND AND OBJECTIVE:

The efficacy of laser treatment of port wine stains (PWS) has been shown to be highly dependent on patient-specific vasculature. The effect of tissue structure on optical and thermal mechanisms was investigated for different pulse durations by using a novel theoretical model that incorporates tissue morphology reconstructed tomographically from a PWS biopsy.

STUDY DESIGN/MATERIALS AND METHODS:

An optical-thermal numerical model capable of simulating arbitrarily complex, three-dimensional tissue geometries was developed. The model is comprised of (1) a voxel-based Monte Carlo optical model, (2) a finite difference thermal model, and (3) an Arrhenius rate process calculation to predict the distribution of thermal damage. Simulations based on previous computer-based reconstruction of a series of 6 microm sections from a PWS biopsy were performed for laser pulse durations (taup) of 0.5, 5.0, and 10.0 ms at a wavelength of 585 nm.

RESULTS:

Energy deposition rate in the blood vessels was primarily a function of vessel depth in skin, although shading effects were evident. Thermal confinement and selectivity of damage were seen to be inversely proportional to pulse duration. The model predicted blood-specific damage for taup = 0.5 ms, vascular and perivascular damage for taup = 5 ms, and widespread damage in superficial regions for taup = 10 ms. The effect of energy deposition in the epidermis was most pronounced for longer pulse durations, resulting in increased temperature and extent of damage.

CONCLUSION:

Pulse durations between 0.5 and 5 ms are likely optimal for the PWS analyzed. The incorporation of a tomographically reconstructed PWS biopsy into an optical-thermal model represents a significant advance in numerical modeling of laser-tissue interaction.

• Authors: T J Pfefer, J K Barton, D J Smithies, T E Milner, J S Nelson, M J van Gemert, A J Welch
• Journal: Lasers in surgery and medicine (Lasers Surg Med) Vol. 24 Issue 2 Pg. 151-66 ( 1999) ISSN: 0196-8092 [Print] United States
• PMID: 10100653 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Topics

• Adult
• Biopsy
• Computer Simulation
• Dermatologic Surgical Procedures
• Female
• Humans
• Image Processing, Computer-Assisted
• Laser Therapy
• Port-Wine Stain (pathology, surgery)
• Skin (pathology)