Simultaneous optimization of cryoprobe placement and thermal protocolfor cryosurgery

Abstract

We demonstrate that it is possible to simultaneously optimize multiplecryoprobe placements and their thermal protocol for one freeze-thaw cycle. Anumerical optimization algorithm is used and three different forms ofobjective function are examined in terms of algorithm convergence rate,minimum value of the chosen objective function, temperature-volume histogramsand isotherm distributions. The optimization results depend on the initialvalues of the variables, the form of the objective function, optimizationgoals and the mathematical method adopted for gradient calculation. Theproposed optimization model offers significant advantages over the previouslyreported semi-empirical approach to conformal cryotherapy, such as the abilityto handle an unlimited number of variables and eliminating the need for theuser input between iterations, thereby reducing, if not removing, thesubjectivity of cryosurgery treatment planning.