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 4-37. Optionally a damage model can be defined to take into account overheating or freezing in tissues, by adding a Thermal Damage subnode.
Model Input
This section contains fields and values that are inputs for expressions defining 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 defined in a material is used. On the material frame, the density is evaluated in relation to a reference temperature in order to ensure conservation of the mass in the presence of temperature variations. By default the Common model input is used. This corresponds to the variable minput.Tempref, which is set to 293.15 K by default. To edit it, click the Go to Source button (), and in the Default 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.
This model input does not override the Reference temperature Tref set in the Physical Model section of the physics interface, which is used to evaluate the reference enthalpy, and a reference density for incompressible nonisothermal flows.
Temperature
This section is available when material properties are temperature-dependent. 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 Default 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 Full based on the characteristics of the thermal conductivity and enter another value or expression in the field or matrix.
When the material and spatial frames differ (due to the presence in the model of a Moving Mesh node, or a Solid Mechanics physics interface for example), you can select on which frame the thermal conductivity is specified.
By default the Deformation model for thermal conductivity is set to Standard. With this option, the thermal conductivity is supposed to be given on the material frame. If the material frame does not coincide with the spatial frame, a conversion is applied to get the variables ht.kxx, ht.kyy, and so on. This option is often suitable for moderate elastic strains.
By selecting the Large strain option, the thermal conductivity is supposed to be given on the spatial frame. In case of isotropic materials, the thermal conductivity variables ht.kxx, ht.kyy, and so on, are directly equal to the values you have set. In case of anisotropic materials, the rotation of the material is also taken into account following
where R is the rotation matrix between the material and the spatial frames.
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.
•
Theory for Bioheat Transfer
•
Bioheat
•
Thermal Damage
There are specific predefined materials available in the Bioheat material database. See Materials Overview and Bioheat Materials Library 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
Heat Transfer in Solids and Fluids>Specific Media>Biological Tissue
Heat Transfer in Solids>Specific Media>Biological Tissue
Heat Transfer in Fluids>Specific Media>Biological Tissue
Heat Transfer in Porous Media>Specific Media>Biological Tissue
Heat Transfer in Building Materials>Specific Media>Biological Tissue
Bioheat Transfer>Specific Media>Biological Tissue
Ribbon
Physics tab with Heat Transfer in Solids and Fluids, Heat Transfer in Solids, Heat Transfer in Fluids, Heat Transfer in Porous Media, Heat Transfer in Building Materials or Bioheat Transfer selected:
Domains>Specific Media>Biological Tissue