MODELING OF INTRALUMINAL HEATING OF BIOLOGICAL TISSUE - IMPLICATIONS FOR TREATMENT OF BENIGN PROSTATIC HYPERPLASIA

A computer model for predicting the thermal response of a biological t issue to different intraluminal heating modalities is presented. A pra ctical application of the model is to calculate the temperature distri butions during thermal coagulation of prostate by contact heating and radiative heating. The model uses a two-dimensional axisymmetric diffu sion approximation method to calculate the light distribution during r adiative heating. The traditional Pennes' bio-heat equation is used to calculate the temperatures in the presence of blood flow. An implicit finite difference scheme with nonuniform grid spacings is used to sol ve the diffusion equation for light distribution and the bio-heat equa tion. Model results indicate that the radiative heating of prostate by Nd:YAG (1064 mm) and diode (810 mm) lasers can be a more effective an d efficient means of coagulating a large volume of prostate, as compar ed to contact heating of the tissue. Blood perfusion is shown to provi de a considerable heat sink as the laser exposure time is increased. S urface cooling by irrigation during the laser irradiation of tissue is shown to be an effective method for delaying tissue explosion and obt aining a large volume of coagulated tissue. The model also shows that the volume of the coagulated tissue is appreciably altered by a change in the rate of energy deposition.