The need for extensive data on the dielectric properties of
human tissues is often and strongly felt among scientists and
researchers involved in the interactions of electromagnetic (EM)
fields and biological systems.
Numerical dosimetry, for instance, (the discipline devoted
to calculate, by means of numerical algorithms, current densities
and specific absorption rates (SARs) in tissues and organs of
individuals exposed to EM fields) deals with digitized 2D or
3D human models each element of which (pixel in 2D and voxel in
3D models) has to be recognized as being constituted by a given,
well defined tissue and thus must have assigned unique dielectric
properties, consisting of a pair of values, one for the relative
permittivity and one for the electrical conductivity
at each frequency of interest.
This application is aimed to calculate the dielectric properties
of human body tissues in the frequency range from 10 Hz to 100 GHz
using the parametric model and the parameter values developed by
C.Gabriel and collegues (see Credits and
References below).
It is based on a client-server approach.
The server program runs in background on a central system and
is responsible for the management of the parameter database (14
parameters for each defined tissue) and for the calculation of the
dielectric properties of requested tissues at requested frequencies.
These properties comprise the relative permittivity, the electrical
conductivity and a few significant derived quantities: the loss tangent,
the wavelength and the penetration or "skin" depth.
The client program is executed by the user on a remote system
connected to the server by a Local or a Wide Area Network supporting the
TCP/IP protocol; the client program implements the user interface and
translates user requests into commands for the server; it also has to deal
with reception and display of the requested data.
The main advantage of the client/server approach consists in the
centralized management of the tissue parameters, allowing
new tissues to be defined or parameter values to be changed
without having to redistribute software to the users.
The users, on their sides, get also rid of the need to implement
the code for the calculation of the dielectric properties from the
parameter values.
The availability of the server documentation
makes it possible, for users who need it and can afford it, to develop
their own applications devoted to specific tasks or platforms.
The reverse of the medal obviously is the need of a TCP/IP link between
the client and the server.
Text mode Win32 standalone applications A few Win32 client applications developed
to demonstrate the remote calculation of the
tissue dielectric properties. Please feel free to
download and save or directly execute them. For what
concerns the source code, please contact me if
you think it could help you.
All Tissues - Single Frequency For the calculation of the dielectric properties of
all the tissues defined in the server at a single frequency.
Single Tissue - Full Span For the calculation of the dielectric properties of
a single tissue over the full frequency span managed by the
server (this span goes from 10 Hz up to 100 GHz in 10 decades,
with 5 calculated points per each decade).
Credits
This application has been prepared at IFAC-CNR (ex IROE-CNR)
as a side project among the activities of the research line
devoted to "Protection against exposures to low-frequency,
radiofrequency and microwave electromagnetic fields".
It would not have been possible without the huge work of C.Gabriel
and collegues at the Brooks Air Force Base (USA), who developed the
parametric model for the calculation of the dielectric properties
of body tissues we use here (see References
below).
At IFAC-CNR, the following people took part in the project:
Research and critical review of bibliographic data on the
dielectric properties of body tissues.
References
International
K.S.Cole and R.H.Cole: "Dispersion and absorption in
dielectrics: I. Alternating current characteristics.",
Journal of Chemical Physics, April 1941, pp.341-351.
C.Gabriel: "Compilation of the dielectric properties of body
tissues at RF and microwave frequencies", Report N.AL/OE-TR-
1996-0037, Occupational and environmental health directorate,
Radiofrequency Radiation Division, Brooks Air Force Base,
Texas (USA), June 1996.
C.Gabriel, S.Gabriel and E.Corthout: "The dielectric
properties of biological tissues: I. Literature survey",
Phys. Med. Biol. 41 (1996), 2231-2249.
S.Gabriel, R.W.Lau and C.Gabriel: "The dielectric properties
of biological tissues: II. Measurements in the frequency range
10 Hz to 20 GHz", Phys. Med. Biol. 41 (1996), 2251-2269.
S.Gabriel, R.W.Lau and C.Gabriel: "The dielectric properties
of biological tissues: III. Parametric models for the
dielectric spectrum of tissues", Phys. Med. Biol. 41 (1996),
2271-2293.
