Biomedical Engineering Reference
In-Depth Information
balloon membrane is then partially inflated against the resistance of the
obstruction. Figure 6.18b illustrates the measurement of the radius (configu-
ration) of the balloon by measurement of the microwave signal reflected from
the antenna (
S
11
). As depicted in Figure 6.18
b
, the expansion of the balloon
might be insufficient, indicating that further treatment is required. Further
inflation of the balloon and additional microwave radiation at the same power
level or higher are depicted in Figure 6.18
c
. Figure 6.18
d
illustrates a condi-
tion in which the power was turned off as a consequence of the desired
opening having been achieved using
S
11
as a guide. Figures 6.19
a
,
b
depict
S
11
0
-10
-20
-30
49
1000
2000
3000
Frequency (MHz)
(a)
4000
5000
0
.
-10
.
-20
-30
max
Medium
inflation
(b)
min
FIGURE 6.19
(
a
)
S
11
measurements. (
b
)
S
11
versus balloon inflation.
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