Biomedical Engineering Reference
In-Depth Information
45
40
35
30
25
Reversible
Irreversible
20
15
10
5
0
1
2
3 4 5
Number of electroporation pulses
6
7
8
FIGURE 2.5
Change in rat liver conductivity during a series of eight electroporation pulses.
The change is expressed in terms of the mean change in tissue conductivity
as percentage of the initial conductivity. Two electric fields were used: one for
reversible electroporation at 450 V/cm and one for irreversible electroporation
at 1,500 V/cm.
phase for various current injections. The measurements would then be used
to calculate the conductivity distribution in the tissue using the conventional
EIT algorithms.
Currently there are no reliable models to predict the increase in conductiv-
ity as a function of the electroporation parameters. As a first estimate we rely
on empirical data that were published for reversible and irreversible electro-
poration in rat liver (Ivorra and Rubinsky 2007). In this study, rat liver tissue
were exposed
in vivo
to nearly uniform electric fields and the changes in con-
ductivity were measured. The researchers used eight electroporation pulses
and recorded the measurements after every pulse. Two groups of rats were
tested, one with electroporation pulses that were designed to cause reversible
electroporation and were set to 450 V/cm and the other group designed to
cause irreversible electroporation with the electric field set to 1,500 V/cm.
Figure 2.5 depicts the results of these tests showing the mean change in
conductivity for each group after every pulse from the electroporation pro-
tocol. The pulses were applied at intervals of 0.5 sec, and each pulse lasted
100
sec.
These results give some idea about the extent of changes in conductiv-
ity we may expect from a similar electroporation protocol. Nevertheless, an
in vivo
medical application would ordinarily make use of nonuniform electric
fields because of the diculty in creating uniform fields with a minimally
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