RF/Microwave Delivery Systems for Therapeutic Applications - RF/Microwave Interaction with Biological Tissues - page 291

Tension gauge

Solder sample

Syringe pump

FIGURE 6.22 Apparatus for tension strength measurements.

Bench-Top Tests The objective of these tests was to determine the strength
of the biological solder. The biological solder was primarily an albumin solu-
tion. The concentration of the albumin tested was 30, 40, and 50%. The mate-
rials added to the albumin solution were silk thread, silk thread with knots,
gauze, or sponge. A Tissue-Tek II disk (25

¥ 20 ¥ 5mm 3 ) was used to contain

1 mL of albumin solution.
After microwave heating, the sample was cut in a 1-cm width and the
tension strength was measured by the apparatus depicted in Figure 6.22. Via
a syringe pump, water was infused into a bucket suspended from the biologi-
cal solder sample. While the tension was recorded, water was infused until the
sample ripped apart (tear strength).
From in vitro experiments we found that 40% chicken albumin solution had
the highest tear strength. Then a 40% albumin solution with different materi-
als [silk threads (al

+ silk), knotted silk threads (al + sk + n), sponge (al + sp), and

a gauze (al gauz)] was used. Among the materials added, we found that a

40% albumin solution combined with sponge had the highest tear strength
(Fig. 6.23).

+

Doping Biological Solder To create tissue anastomoses with microwaves, the
tissue temperature must be kept below the threshold for damage, while the
biological solder is heated above 60°C. This process is depicted in Figure 6.24
for an arterial anastomosis. The microwave antenna is positioned inside the
artery, and solder is placed on the outside of the vessel and in any small gap
between the arteries. The graphs on the left side show the desired
temperature profiles. If microwaves heated by convection, these temperature