Biomedical Engineering Reference
In-Depth Information
R
lim
[
mm
]
60
50
40
Cr
=
15
.
4
30
20
10
0
0
0.01
0.02
0.03
0.04
0.05
v
eff
[1]/sec
FIGURE 1.16
Effects of the perfusion rate on the limiting radius.
blood circulatory system. The resulting model, under appropriate conditions,
naturally reduces to those introduced by Chato, Bejan, Keller, and Seiler and
Weinbaum and Jiji for countercurrent heat transfer for the case of closely
aligned pairs of vessels.
As for an application of the bioheat equation, the freezing process within
a tumor during cryoablation therapy was investigated both analytically and
numerically. The freezing front in a tumor during percutaneous cryoablation
was traced exploiting the bioheat equation. It has been found that there exists
a limiting size of the tumor that one single cryoprobe can freeze at the maxi-
mum. An excellent agreement between the analytical and numerical results has
been achieved for the time required to freeze the tumor using the cryoprobe
of one single needle. The resulting analytical expression for estimating the
limiting radius provides useful information for cryotherapy treatment plans.
1.9
Nomenclature
A
Surface area (m
2
)
a
f
Specific surface area (1/m)
Interface between the fluid and solid (m
2
)
A
int
b
ij
Forchheimer tensor (1/m)
c
p
Specific heat at constant pressure (J/kg K)
Cr
Dimensionless parameter associated with the thermal
conductivity ratio
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