| Abstract |
Photodynamic therapy is a method in ophthalmology used to destroy partially the ciliary body, with the intention of reducing the intraocular pressure. The method may be optimized in laboratory rabbits. For example, it is possible to radiate different individuals under different initial conditions, such as dose of, time and intensity, until the desired response is achieved. Some of these conditions affecting the results of the experiment, for example the dose of photo-sensitizer agent and the radiation time, can be deduced to the needs of human patients. However, it is impossible from such experiments to calculate the radiation distribution resulting in the human ciliary body, since the human sclera has a different thickness than that of a rabbit. As it is clear that such experiments can not be undertaken in human subjects, an arithmetical model estimating the distribution of the radiation exiting the human sclera would prove very useful in optimizing photodynamic treatment. Such a model was created using the Monte Carlo method, which is an arithmetical method creating random initial conditions, which are then observed until the conclusion of the phenomenon. In the present study, the method creates an energy packet for every photon that enters the sclera which is altered by a random angular density probability and is being observed until the photon exits the sclera either from the front side, i.e. the side of the ciliary body, or the rear side, i.e. the side which the fiber optic is located. In order to validate this method, a series of experiments were undertaken using eyes of swine, which were irradiated with a diode laser and the distribution of the radiation was measured when it exited the tissue. Then an effort was made to image this distribution by the arithmetical model, using a series of different angular density probabilities until achieving the desirable distribution image. Based on the results of the study, it was concluded that the created arithmetical model was capable of predicting the distribution of the radiation exiting the tissue, for a variety of sclera thicknesses. It is expected that the model will contribute to the optimization of the application of photodynamic therapy.
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Χρήση της μεθόδου Monte Carlo για τον υπολογισμό παραμέτρων της διασκληρικής ακτινοβόλησης του ακτινωτού σώματος με διοδικό laser
