Stephanos Papademetriou

Numerical simulations of a diode laser BPH treatment system

Numerical simulations are presented of the laser-tissue interaction of a diode laser system for treating benign prostate hyperplasia. The numerical model includes laser light transport, heat transport, cooling due to blood perfusion, thermal tissue damage, and enthalpy of tissue damage. Comparisons of the stimulation results to clinical data are given. We report that a reasonable variation from a standard set of input data produces heating times which match those measured in the clinical trials. A general trend of decreasing damage volume with increasing heating time is described. We suggest that the patient-to-patient variability seen in the data can be explained by differences in fundamental biophysical properties such as the optical coefficients. Further work is identified, including the measurement and input to the model of several specific data parameters such as optical coefficients, blood perfusion cooling rate, and coagulation rates.

Electromagnetic frequency considerations for the generation of heat for thermotherapy

Many novel treatments for BPH are predicated on depositing power, for example using a laser, microwave, or rf source, to generate heat. In order to be useful and effective a requisite amount of power must be deposited in the tissue so that a reasonable amount of tissue can be necrosed in a reasonable time. The potential to be effective is fundamentally effected by the electromagnetic frequency. The frequency of the power source dictates the penetration characteristic in tissue, and thus the size of the heat source that can subsequently conduct further into the tissue. Because tissue char limits the peak temperature accessible for any power source, a particular frequency can only effectively heat a certain amount of tissue, given similar conditions. Too large a penetration of power can be as ineffective as too shallow.