Biological Tissue
This node adds the bioheat equation as the mathematical model for heat transfer in biological tissue. This equation can include source terms representing blood perfusion and metabolism using Pennes’ approximation, through the addition of a Bioheat subnode; see Equation 4-19. Optionally a damage model can be defined to account for overheating or freezing in tissues, by adding a Thermal Damage subnode.
Model Input
This section has fields and values that are inputs to expressions that define material properties. If such user-defined property groups are added, the model inputs appear here.
Volume reference temperature
This section is available when a temperature-dependent density is used. On the material frame, the density is evaluated onto a reference temperature to ensure mass conservation in the presence of temperature variations. By default the Common model input is used. This corresponds to the variable minput.Tempref, which is set by default to 293.15 [K]. To edit it, click the Go to Source button (), and in the Common Model Inputs node under Global Definitions, set a value for the Volume reference temperature in the Expression for remaining selection section.
The other options are User defined and all temperature variables from the physics interfaces included in the model.
Temperature
This section is available when temperature-dependent material properties are used. By default the temperature of the parent interface is used and the section is not editable. To edit the Temperature field, click Make All Model Inputs Editable (). The available options are User defined (default), Common model input (the minput.T variable, set to 293.15 [K] by default) and all temperature variables from the physics interfaces included in the model. To edit the minput.T variable, click the Go to Source button (), and in the Common Model Inputs node under Global Definitions, set a value for the Temperature in the Expression for remaining selection section.
Heat Conduction, Solid
The default Thermal conductivity k uses values From material. For User defined select Isotropic, Diagonal, Symmetric, or Anisotropic based on the characteristics of the thermal conductivity and enter another value or expression in the field or matrix.
Thermodynamics, Solid
The default Density ρ and Heat capacity at constant pressure Cp are taken From material. See Material Density in Features Defined in the Material Frame if a temperature-dependent density should be set.
The heat capacity describes the amount of heat energy required to produce a unit temperature change in a unit mass.
For User defined enter other values or expressions.
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Theory for Bioheat Transfer
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Bioheat
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Thermal Damage
When Surface-to-surface radiation is activated, the Opacity (Surface-to-Surface Radiation interface) subnode is automatically added to the entire selection, with Opaque option selected. The domain selection can’t be edited. To set some part of the domain as transparent, add a new Opacity (Surface-to-Surface Radiation interface) subnode from the context menu (right-click the parent node) or from the Physics toolbar, Attributes menu.
There are specific predefined materials available in the Bioheat material database. See Materials Overview and Bioheat Materials Database in the COMSOL Multiphysics Reference Manual.
Hepatic Tumor Ablation: Application Library path Heat_Transfer_Module/Medical_Technology/tumor_ablation
Microwave Heating of a Cancer Tumor: Application Library path Heat_Transfer_Module/Medical_Technology/microwave_cancer_therapy
Modeling a Conical Dielectric Probe for Skin Cancer Diagnosis: Application Library path Heat_Transfer_Module/Medical_Technology/conical_dielectric_probe
Location in User Interface
Context menus
 Bioheat Transfer>Biological Tissue
More locations are available if the Heat transfer in biological tissue check box is selected under the Physical Model section. For example:
Heat Transfer in Solids>Biological Tissue
Ribbon
Physics Tab with interface as Heat Transfer, Bioheat Transfer, Heat Transfer in Solids, Heat Transfer in Fluids, Heat Transfer in Porous Media or Heat Transfer in Building Materials selected:
Domains>interface>Biological Tissue