Mathematical modeling of temperature mapping over skin surface and its implementation in thermal disease diagnostics

A thermal-ablation bioheat model including liquid-to-vapor phase change, pressure- and necrosis-dependent perfusion, and moisture-dependent properties

Advancement of the recent micro/nanotechnology stimulates the renaissance of using magnetic micro/nanoparticles embedded in tissues for the target tumor hyperthermia. However, there is a strong lack of quantitative understanding of the temperature profiles thus induced by the applied external electromagnetic (EM) field, which may impede the successful operation of this therapy. In the current study, the three-dimensional quasi-steady-state EM field and transient tissue temperature behavior induced by two planar electrodes were numerically investigated. Detailed computations indicated that nanoparticles exhibit an extraordinary highly focused heating on target tumor tissue, which is much stronger than that in the surrounding areas. This heating effect depends heavily on the properties of the magnetic nanoparticles, which may vary appreciably for different samples depending on their particle sizes and microstructures. The effect of micro/nanoparticle concentration, heating area, and the frequency and strength of the external alternating EM field were also tested. Moreover, a criterion to determine the appropriate particle concentration thermally important for medical treatment was established. Given accurate thermal and EM parameters for cancerous tissue embedded with nanoparticles, the current model could possibly be applied in the hyperthermia treatment planning and help optimize the surgical procedures.

3-D numerical study on the induced heating effects of embedded micro/nanoparticles on human body subject to external medical electromagnetic field

Recently, a new tumor ablation modality based on freezing immediately followed by a rapid and strong enough heating has been proved to be more effective and flexible than conventional cryosurgery. In this study, a numerical algorithm based on the effective heat capacity method is established to solve three-dimensional (3-D) phase-change problems of biological tissues subject to combined freezing and heating. The accuracy of the numerical code thus compiled is validated through comparisons of the calculation results with a 1-D exact solution for a semi-infinite region solidification problem. Using the present algorithm, comprehensive analysis is performed on the freezing/thawing behavior of biological tissues with tumors. For treatment of large tumors, where strong cooling/heating power is required, a single probe will not be able to address a sufficiently large volume. For this case, freezing/heating problems using a three-probe system are solved for illustration purposes. The present algorithm is expecte...

Numerical simulation of 3-d freezing and heating problems for combined cryosurgery and hyperthermia therapy

The main difficulties encountered in cryosurgery are the unknowns on the extent of the irregular shape of the frozen region, the direction of ice growth, and the temperature distribution within the ice balls during the freezing process. In this study, a numerical algorithm based on the dual reciprocity boundary element method (DRBEM) is developed to solve multidimensional phase change problem of biological tissues subject to cryosurgery. The tissues are treated as nonideal materials, freezing over a temperature range, and the effects of blood perfusion and metabolic heat generation in the unfrozen tissues are also taken into account in the heat transfer model. The accuracy of this DRBEM algorithm is validated through comparisons of the calculation results with the one-dimensional numerical solutions by the finite difference method. Comprehensive analyses are performed respectively, on the freezing behaviors of normal biological tissue and diseased tissue with tumors. For treatment of large tumors where large cooling power is required, a single probe will not be able to address a sufficiently large volume. On this account, the freezing problems by two- and three-cryoprobe system are solved for illustration purpose. The present algorithm can serve as a useful tool for post-treatment planning in cryosurgery.

Modeling of multidimensional freezing problem during cryosurgery by the dual reciprocity boundary element method

The Monte Carlo method is implemented to solve the direct bioheat transfer problems, which are often encountered in the treatment planning of cancer hyperthermia. Several algorithms were developed to solve for the temperature transients inside the biological bodies with various time or space-dependent boundary conditions, blood perfusion, metabolic rate, and volumetric heat source for the tissues. The computer code thus compiled was validated through comparison with a theoretical solution. To illustrate the applications of the present numerical strategy, heat transfer in several three-dimensional cases was particularly studied. Parametric calculations were performed to test the technical adaptability of the present Monte Carlo algorithms. Some mathematical issues thus raised are discussed.

Zhong-Shan Deng

Papers

Monte carlo method to solve multidimensional bioheat transfer problem