Pulse Laser Parameters Effect on Tissue Thermal Damage Zone in Coagulation Process


Owed to wide use of pulsed lasers in a medical field, a deep understanding oftheir effects on the temperature increase in tissue and the subsequent tissue thermaldamage in a coagulation process may be a matter of importance. The influence oflaser beam profile, repetition rate and pulse width on temperature distribution and thesubsequent thermal damage in tissue are studied using finite element method, whichsolves the axis-symmetry bio-heat equation in tissue subjected to far IR pulse laserirradiation. Some conclusions are obtained: as energy/pulse remains constant,Gaussian laser beam profile rather than a top-hat beam will increase the in-depthtissue thermal damage at and near the center of the spot region, increasing inrepetition rate will increase the temperature distribution and subsequent damage zone.As pulse width decrease, high temperature may be reached leading to cause aquantitatively and qualitatively damage which can be recognize as an increase in thesize of the damage zone and a higher value of thermal dose. An increase in pulsewidth will reduce the rate at which energy deposed in the tissue which result in lowextent of temperature increase which result in reduction of the damage zonequantitatively and qualitatively.