Biomedical Engineering Reference
In-Depth Information
1
E
=
0.5
E
= 0.25
a
v
TT
−
−
L
L
a
v
TT
N =
0.5,
n =
5
0
E
= 0
E
=
0.5
0.5
E
=
0.25
v
v
−
−
TT
TT
L
E
=
0
a
v
0
L
0
0
0.5
1
x
/
L
(a)
1
E
=
0.5
a
v
−
−
TT
E
= 0.25
L
L
a
v
TT
0
E
= 0.5
E
=
0
0.5
E
= 0.25
E
=
0
v
v
TT
TT
−
−
L
a
v
0
L
N =
0.5,
n =
5
0
0
0.5
1
x
/
L
(b)
FIGURE 1.8
Arterial and venous blood temperature profiles along the vessel axes for the
case of
n
= 5 (a)
N
=0
.
5,
n
= 5 and (b)
N
=1
.
0,
n
=5.
significant acceptance as minimally invasive therapy for treatments of various
malignant cancers. In a cryosurgical treatment, a single or multiprobe metal
system is placed in contact with the target tissue through the skin. We have
placed the emphasis of this paper upon the treatment of malignant lung tumor,
since its application to lung cancer has been practiced on a trial basis for some
years in Japanese medical schools (Nakatsuka et al. 2004).
The cryoprobe in consideration houses a small coaxial nozzle internally.
A high-pressure gas supply line is connected to the probe so as to supply
Argon gas, which expands through the nozzle to the probe tip and then flows
backward through the internal channel leading to the cryoprobe outlet. Owing
to the Joule-Thompson effect, the outer surface temperature of the probe
decreases below
135
◦
C. As the tissue temperature is lowered, an ellipsoidal
ice ball forms around each probe increasing in size, eventually encompassing
and invading the entire tumor. This freezing process continues for 5-15 min.
Then, the thawing process takes place as supplying Helium gas. Because of
−
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