Human Material Properties Macro

Under "Home: Macros->Macros->Materials->Define Human Material Properties" you find a macro which allows you to easily choose any required frequency for the properties of biological materials in the CST Voxel Family. The new material definition can then be seen in the navigation tree and if necessary also be modified to specific requirements.

Evaluation Frequency (MHz)

The Biological material properties will be recalculated using the 4-Cole-Cole formulation at the specified frequency. The formula and parameters used are found under http://niremf.ifac.cnr.it/docs/DIELECTRIC/AppendixC.html.

Use age correction for fetus

When it is detected that the model contains a fetus, then the user can specify that age correction be used for the properties of the fetus. When selected, all materials of which the names start with the word "fetus" and also the Umbilical Cord and Placenta will be allocated the material properties equivalent to 0.01 years of age.

Consider age Properties

Use this option for all biological tissues (excluding Fetus, umbilical Cord and Placenta), when age adjustment is required, i.e. for Baby or Child model. It is recommended if the subject is younger than 7 years old. Age is adjusted according to Ref.1.

Since the amount of water in biological tissues varies as a function of age, the complex permittivity for younger tissues can be estimated if the Total Body Water (TBW) of the material is known. If the water content is low like i.e. in bone, the adjustment is not necessary and the user will obtain a message stating that these materials were not changed.

The above equation makes use of the dielectric constant of water. Unlike the reference Ref.1, the macro also calculates a frequency dependent dielectric constant for water.

Including own materials

The user can include his/her own materials, by editing the file "Material_Map.xlsx" located in the "Library/Bio Models" directory of the CST STUDIO SUITE installation. Add the material name, which is listed in the Navigation Tree of CST MWS, to Column A of this spreadsheet. Please note that the name in the Navigation Tree has to be identical to the name in Column A.

A mapping to the materials listed in Row 1 has to be performed. Note that the mapping has to add up to 1.

For example, if the user has a material called "Woman_Blood", which is not found in the standard CST material database, then this can be added to column 1. Since the blood of a woman is identical to "Blood", it is then necessary to map "Woman_Blood" to "Blood", as it appears in Row 1.

When completed, the spreadsheet needs to be saved as a "Comma-Separated Values" (CSV) file in the same directory as the original spreadsheet.

References

Ref.1.: "Jianqing Wang, 'Approximation of Aging Effect on Dielectric Tissue Properties for SAR Assessment of Mobile Telephones', IEEE Transactions on Electromagnetic Compatibility, Vol. 48, No. 2, May 2006"