Biomedical Engineering Reference
In-Depth Information
b. Cytotoxicity test
c. Thrombogenicity test
d. Hemolysis (breaking red cells) test
e. Genotoxicity test
ii. Material verification
iii. Heavy metals
iv. Leachables
B.
Sterility
i. EtO residuals outgas time
ii. Sterile cycle
iii. Pyrogen-pyrogen inhibition: detects bacterial endotoxins
iv. Bioburden and spore recovery: natural microbial population of
product (quarterly monitoring program)
C.
Shelf life: 6 months from date of manufacture
6.2.2
Circular Waveguide [7-9]
Fundamentals
A catheter, that is, a cylindrical tube made of plastic
(Fig. 6.3
a
), can become a circular waveguide when the inside of the wall is
metallized. When filled with a material with e close to that of deionized
water having dielectric constant of 80, this metallized tube becomes a
loaded, thus reduced waveguide. Although not utilized in our experiments (but
used by others), for the sake of completeness it is worthwhile analyzing the
capabilities of the
metallized catheter
that becomes a transmission medium for
EM energy.
The dominant mode in a circular waveguide is the TE
11
mode. This mode
is shown in Figure 6.3
b
, along with a number of other possible modes of trans-
mission. The field equations are expressed by using the cylindrical coordinate
system for the TE
11
wave (dominant mode).
In the following equations,
B
is an arbitrary constant determining ampli-
tude,
J
1
(·) is the Bessel function of the first order, w is the circular oscillation
frequency of an EM field,
c
is the speed of light, and
a
is the radius of a cir-
cular tube:
Ju
r
a
Ê
Ë
ˆ
¯
H
=
¢
cos
q wb
cos
(
t
-
z
)
z
1
,
1
HB
a
u
b
Ju
r
a
Ê
Ë
ˆ
¯
(
)
=
¢
cos
qwb
sin
t
-
z
r
1
,
1
¢
11
,
HB
a
ur
b
2
Ju
r
a
Ê
Ë
ˆ
¯
=
¢
sin
qwb
sin
(
t
-
z
)
(6.4)
q
1
,
1
2
()
11
,
m
w
b
m
w
b
E
=
0
E
=
H
E
= -
H
(6.5)
z
r
q
q
r
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