Influence of prostatic blood flow on laser prostatectomy

Normally, a laser prostatectomy to treat Benign Prostatic Hyperplasia (BPH) is performed using a fixed dosimetry. Differences in, e.g., blood flow, optical properties and geometry, are not taken into account, although most of these differences may be distinguished when performing a cystoscopy, e.g., the color of the prostate. These characteristics show their influence in the final tissue effect. We developed a model to predict the permanent damage to the tissue. A Monte Carlo simulation program was used to calculate the light distribution in the prostate due to Nd:YAG laser light irradiation. Consequently, using the absorbed energy as a heat source, the thermal distribution in the tissue was computed using the method of finite differences. This numerical model was combined with a rate process damage model (Henriques equation) to make it possible to predict the extent of laser induced permanent damage (denaturation). The model is dynamic in time, which enabled us to observe the evolution of the damage process. In this flexible model blood vessels were incorporated. The blood vessels showed to have major influence on the temperature distribution and on the created damage. The vessels act like a heat sink, which clamps the temperature and shields the heat to penetrate deep into the tissue.