Biomedical Engineering Reference
In-Depth Information
90
10
-3
-1
1
3
X (mm)
(c)
10
90
-3
-1
1
3
X (mm)
(d)
90
10
-3
-1
1
3
X (mm)
(e)
90
10
-3
-1
1
3
X (mm)
(f )
FIGURE 2.9
(
Continued
) Laser beam heating axisymmetric FDM numerical model result. A CO
2
laser (λ = 10.6 μm) at total power of 0.5 W with
Gaussian beam profile, 2σ diameter = 7 mm for 20 s on tissue 2 mm thick with 50% mass fraction water. The effective laser absorption coefficient
was μ
a
= 492 (cm
−1
); and the beam center surface fluence rate 2.59 (W cm
−2
). (a) Beam center surface temperature history; 100°C reached at
t
= 18 s.
(b) Spatial distribution of temperature at the end of heating, 20 s. (c) Apoptosis/necrosis 10% and 90% damage contours. (d) Chinese hamster ovary
cell 10-90% contours. (e) BhK cell 10-90% contours. (f) Microvascular damage 10-90% contours. (g) Cardiac muscle whitening 10-90% contours.
(h) Skin burn coefficient (Diller
(27)
) 10-90% contours. (i) Collagen birefringence loss 10-90% contours. (j) Collagen shrinkage 10-60% contours.
Note that the top center transient temperature follows a
square-root-of-time dependence very closely (Figure 2.9a) and
equilibrium boiling at 100°C commences at about 18 s. In Figure
2.9b, substantial heating occurs throughout the thickness, and
out to a radius of about 3 mm.
Eight Arrhenius integral damage processes (Equation 2.6)
acting in parallel have been included for illustration (Figures
2.9c-j) in the form of the probability of damage,
P
(%), as in
Equation 2.7. In Figure 2.9c, the model predicts that apoptosis/
necrosis damage is not likely be observed in this short heating
