a method for determining a volume of ablated tissue includes the steps of supplying energy to tissue , indicating an axis within the tissue , and simulating slicing of the tissue substantially perpendicular to the axis to obtain a plurality of simulated slices . each of the plurality of simulated slices has a thickness , a cross - sectional perimeter , and a trajectory point defined by the axis within the tissue . the method further includes the steps of determining a volume of each of the plurality of simulated slices based on the trajectory point , the cross - sectional perimeter , and the thickness of each simulated slice , and summing the volumes from each of the plurality of simulated slices to obtain the volume of the ablated tissue .