20pt THERMAL MODEL PREDICTIONS OF ULTRASONIC LESION FORMATION

Blood ow can e ect temperature distributions of heated tissues. In this work the e ects of microvascular cooling on temperature distributions during ultrasonic lesioning are examined. Microvascular cooling was assessed using two simple thermal models used in hyperthermia treatment planning: the Pennes Bioheat Transfer Equation (BHTE) and the scalar E ective Thermal Conductivity Equation (ETCE). The equations of heat transfer in perfused tissues were solved by nite di erences in cylindrical coordinates. The extent of the lesioned tissue was determined by the accumulated thermal dose at each location. The size of the lesion was then calculated from the boundaries of the thermal isodose curves generated by the simulations. The model of bioheat transfer used can strongly in uence simulation outcome. Even for short exposure times of ultrasonic heating, blood ow may be a signi cant determinant of the lesion shape and size.