Biomedical Engineering Reference
In-Depth Information
65
55
45
35
Sim
Seq
Acid
FIGURE 19.8
Average temperature graphed as a function of method of injection. Simultaneous injections produced the highest average and peak
temperatures compared to sequential injection. Reagents were used at a concentration of 10 mol/L.
from a sphere. To our surprise, the ratios of the different methods
were not significantly different and were reasonably high.
Finally, there is the question of total volume. Here there
was no question that the volume of coagulation obtained with
sequential injection was clearly the greatest among all the con-
ditions tested. However, as noted before, this was not tolerated
nearly as well physiologically. In both methods, the volume was
a large improvement over the use of acid alone.
The CT imaging of the explants proved disappointing, with
a relatively poor correlation between distribution on imag-
ing and what was found on sectioning (Figure 19.10a and b).
The distribution of contrast within the tissues was uneven and
did not track closely enough to the pathology to be useful. The
correlation was closer with acid alone, as mentioned earlier.
Histologically, coagulative necrosis was quite apparent, illus-
trated in Figure 19.11.
Given that simultaneous injection seemed to be tolerated well
and improved upon use of acid alone, we then investigated the
relationships between both temperature and final volume of
coagulation depending on the concentration of the reagents and
the volume injected. Animals were treated according to a proto-
col in which four identical injections were administered. Each
animal was assigned to a position on a grid using total injection
volumes of 1, 2, and 4 cc. The concentrations used were 5, 10, and
15 M. For statistical considerations, we used four animals in the
center of the grid.
25
20
15
10
5
0
Sim
Seq
Acid
FIGURE 19.9
Comparison of volumes for zones of coagulation among different conditions for acetic acid by itself, simultaneous injection with
sodium hydroxide, and acid injected first followed by sodium hydroxide solution. Acid alone produced the smallest volume, and the volumes
obtained from either of the other methods were larger.
