Biomedical Engineering Reference
In-Depth Information
This offers a much more accurate parametric description of the permeabi-
lization of the tissues during electroporation. The study allows for a macro-
scopic representation of the current-applied voltage relation. The study com-
pares well with experimental findings relating the electrical behavior of the
skin fold at various applied voltages.
The concept of using the electric field magnitude to define the degree of
permeability of the skin and underlying tissue is used the studies by Pavselj
et al. (2005) in which a single value of postelectroporated tissue electrical
conductivity increase is used. The basis of this study is that experimentally
it has been shown that electroporation begins at a specific transmembrane
voltage,
E
0
, but that when a certain voltage is exceeded,
E
1
, irreversible
cellular damage begins. The study relies on experimentally derived values
of
E
0
and
E
1
to represent the threshold values of various tissues undergoing
electroporation. The study models the degree of electroporation by an increase
in local tissue electrical conductivity. Electroporation is modeled as a function
of local electric field—that is the degree of electroporation is represented by
the local increase in magnitude of the electric field.
The electrical conductivity,
σ
(
E
), is related to degree of electroporation
by some relationship between electrical conductivity before permeabilitization,
σ
0
, and a maximum value of electrical conductivity due to electroporation,
σ
1
.
The novel concept of this study is the variety of functional dependencies
that are incorporated to depict the relation between conductivity and poten-
tial drop:
Step function:
σ
(
E
)=
σ
0
E<E
0
(9.28)
σ
1
E
≥
E
0
Linear dependence:
σ
(
E
)=
σ
1
−
σ
0
E
+
σ
0
(9.29)
E
1
−
E
0
Exponential dependencies:
exp
E
−
E
0
−
1
B
exp
E
+
σ
0
σ
(
E
)=(
σ
1
−
σ
0
)
(9.30)
−
E
1
1
−
B
exp
E
−
E
1
−
1
B
exp
E
σ
(
E
)=(
σ
0
−
σ
1
)
+
σ
1
(9.31)
−
E
0
B
−
1
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