Simulation Of Energy Distribution In Intense Pulsed Light Treatment For Port-wine Stains

Port wine-stains are congenital benign tumor begin from skin vessels. It is characterized by the telangiectasias in dermal layer. It always occurs on the face and neck, showing sizes of pink, dark red or purple patches, which brings significant adverse effects to the patients' appearance and psychological. Currently, kinds of laser treatments are the principal treatment means for port wine-stains. However, there are many problems in laser treatment, such as incomplete treatment and production of side effects. So, the laser treatments in clinical and theoretical have also been on studying. Recently, intense pulsed light system is induced to clinical treatment. The main content of this work is to simulate the process of intense pulsed light treatment for port wine-stains.In this thesis, laser-tissue interaction fundamentals are briefly introduced. Selective photothermolysis is the basic principles for the laser treatment, the hemoglobin absorb the light energy and then convert it into heat, which warming the blood vessel to block the flow of blood.This work is to create the multiple layer's skin model with discrete blood vessels; and to simulate the process of photon transport using the Monte Carlo methods. At last, it records the energy distribution of the blood vessels. Then, it simulates the energy distribution under different skin tissue forms.The results demonstrated that, the energy is reduced along the photon propagation direction. The energy near the light source values significantly higher than that on the side away from the light source. Energy in the vascular center is lower than that on the sides. Comparison of the simulation of 577nm laser, the energy distributions in the simulation of the intense pulsed light and 595nm laser are more uniform. And the photons of the intense pulsed light and 595nm laser can achieve greater depth.The results also show that, the size and depth of the blood vessels could make a great impact to the energy distribution. With the same conditions, the energy distribution is more uniform in the small blood vessels. The high energy covers wider in the blood vessels, however the peak energy of the small blood vessels is lower than that in the big blood vessels. It shows that the energy value in the deep blood vessels is much smaller than that in the shallow blood vessels. In the case of coexist of deep and shallow blood vessels, the energy value in the deep vessels is only about 12%of that in the shallow energy. The results also show that the content of melanin in the epidermis has a great influence on the energy into the dermis.