Thermal Modelling for Laser Treatment of Port Wine Stains

549
affects the highest temperature possible in the PWS layer and the evenness of the
temperature distribution over the PWS layer. A much higher possible temperature in PWS is
achieved for the shorter 585 nm laser than that for the longer 595 nm laser. The longer 595
nm laser, however, produces a much more even heating over the PWS layer. This can be
more clearly demonstrated in the case of a thicker PWS layer as shown in Figure 12b. (a) Wavelength: 585nm (b) Wavelength: 595nm
Fig. 11. Temperature distributions within the skin at the end of 1.5 ms laser irradiation.
(PWS layer thickness: 200 μm, laser fluence: 6 J/cm
2
, with CSC)

0 100 200 300 400 500 600
20
40
60
80
100
120
Temperature (
o
C
)
Depth ( μm)
585nm
595nm

. The comparison of the central
temperature profile within skin for three cases is given correspondingly in Figure 13d.

Developments in Heat Transfer

550

(a) Pulse duration: 1.5 ms (b) Pulse duration: 10 ms 0 100 200 300 400 500 600
20
40
60
80
100
120
Temperature (
o
C
)
Depth ( μm)
1.5ms
10ms
40ms
Pulse duration

(c) Pulse duration: 40 ms (d) Central temperature profile
Fig. 13. Calculated temperature distributions within the skin at the end of laser irradiation
for three pulse durations: (a) 1.5 ms, (b) 10 ms and (c) 40 ms; (d) Comparison of the central

primarily a thermal issue involving both radiative energy transport within the tissue during
laser irradiation and tissue heat conduction during and after laser irradiation. Based on
simplified skin models that reduce the complex anatomic structure of skins to simple layer
structures, the process can be successfully simulated by solving the corresponding radiative
energy transport with the multi-layer Monte-Carlo method and the heat conduction
equation with traditional numerical methods. We have used a simple multi-layer
homogeneous model to illustrate the basic thermal characteristics of laser treatment of PWS.
We also demonstrated that the model can be used to make selections of the laser parameters
such as wavelength and pulse width in clinical practice. Quantitative information for critical
surface cooling technique, CSC, is also presented and included in our model.
Although great progresses have been achieved in both clinic practice and physical
understanding of laser PWS after four decades’ efforts, many issues remain. Clinically, the
present protocol of PDL-based lasers could significantly eliminate the PWS vessels, but only
less than 20% of complete clearance of the PWS has been achieved (Kelly et al., 2005).
Recurrence has been observed with a rate up to 50% after five years (Orten et al., 1996). All
these suggest a lack of fundamental understanding of the PWS destruction mechanisms in
the present laser PWS process. From the modeling point of view, neither the multi-layer
homogeneous model nor the discrete blood vessel model provides accurate representation
of the real and complex anatomic configuration of the PWS vessels. Attempts to construct
realistic PWS structure based on computer-reconstructed biopsy from PWS patients had
only limited success (Pfefer et al., 1996). New models are desired that should combine the
simplicity of the multi-layer homogeneous model while take into account the detailed effect
of complex PWS configurations. In addition, quantitative predictions of the temperature
change of the PWS in the laser treatment require accurate optical and thermal properties of
PWS, which are scarce at the moment.
The ultimate objective of any model for laser PWS is to accurately predict the thermal
damage after the laser irradiation. The existing PWS damage model is a pure thermal model
based on simple Arrhenius rate process integral (Pearce & Thomsen, 1995). The model does
not take into account the photochemical and photomechanical effect of laser on skin tissues
and blood vessels. Recent experimental evidence suggests that the vessel damage in laser

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numerical simulation. Lasers in Surgery and Medicine, Vol.38, No.2, (February 2006),
pp. 155-162. ISSN 0196-8092
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Treatment of cutaneous vascular lesions using multiple-intermittent cryogen spurts
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and Medicine, Vol.39, No.6, (July 2007), pp. 494-503, ISSN 0196-8092
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stain treatment. Lasers in Surgery and Medicine, Vol.11, No.6, (October 1991), pp. 601-
605, ISSN 0196-8092
Kelly, K.M.; Choi B.; McFarlane, S; et al. (2005). Description and analysis of treatments for
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287—94, ISSN 1521-2491
Kienle, A. & Hibst, R. (1995). A new optimal wavelength for treatment of port wine stains?
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therapy: a theoretical approach. Phys Med Biol, Vol.30, No.6, (June 1985), pp.573-87,
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Lanigan, S. W. (2000). Lasers in Dermatology, Springer, London, ISBN 1852332778
Li, D.; He, Y.L.; Liu, Y.W. & Wang, G X. (2007a), Numerical analysis of cryogen spray
cooling of skin in dermatologic laser surgery using realistic boundary conditions.

No.11, (November 1996), pp. 1174-9. ISSN 0886-4470 (Print) 1538-361X (Online)
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Thermal Response of laser-Irradiated Tissue, A.J. Welch & M.J.C. van Gemert, (Ed.),
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Pfefer, T.J.; Barton, J.K.; Chan, E.K.; Ducros, M.G.; Sorg, B.S.; Milner, T.E.; Nelson, J.S. &
Welch, A.J. (1996). A three dimensional modular adaptable grid numerical model
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Pfefer, T.J.; Smithies, D.J.; Milner, T.E.; van Gemert, M.J.C.; Nelson, J.S. & Welch, A.J. (2000).
Bioheat transfer analysis of cryogen spray cooling during laser treatment of Port
Wine Stains. Lasers in Surgery and Medicine, Vol.26, No.2, (February 2000), pp. 145-
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of droplet size and spray density on heat removal. Lasers in Surgery and Medicine,
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Zhou, Z.; Xin, H.; Chen, B. & Wang, G X. (2008b). Single Droplet Evaporation Model in
Laser Treatment of PWS in Conjunction with Cryogen Spray Cooling. Proceedings of
2008 International Conference on Bio-Medical Engineering and Informatics, Vol. 1, pp.
551-556, May 28-30, Sanya, Hanan, China, ISBN: 978-0-7695-3118-2
28
Study of the Heat Transfer
Effect in Moxibustion Practice
Chinlong Huang and Tony W. H. Sheu
Dept of Engineering Sciences and Ocean Engineering,
National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617
Taiwan

1. Introduction
“First you use the needle (acupuncture), then the fire (moxibustion), and finally the herbs”
(Tsuei, 1996) has been well known in traditional Chinese medicine (TCM). In fact, moxibustion
has played an important role in Asia for many years (Zhang, 1993). In Huang Di Nei Jing
(Maoshing (translator), 1995), we can find that when needle can’t do a job, moxa is a better
choice. Moxibustion rather than acupuncture was commonly known to be able to alleviate
pains due to some severe diseases, manifested by vacuity cold and Yang deficiency. In
clinical studies, many experiments have confirmed that moxibustion is capable of enhancing
immunity, improving circulation, accommodating nerve, elevating internal secretion and
adjusting respiration, digestion and procreation et al. (Wu et al., 2001; Liu, 1999). However,
moxibustion has not been accepted as the modern therapy because of the lack of standard
practice procedures. In addition, moxibustion is subject to the danger of scalding patients.

needle
needle
handle

(a) (b)
Fig. 1. Schematic of the moxibustions. (a) Direct moxibustion therapy; (b) Warm needle
moxibustion therapy
Another indirect moxibustion involves the use of needles and moxa. One needle, along
which there is a moxa, is inserted into the skin near an acupoint. The moxa cone placed on
the inserted needle is then ignited. The heat generated from the burning moxa will propagate
through the needle and transfers to the acupoint by heat conduction. During the treatment,
a dried moxa is in contact with the handle of the acupuncture needle after the needle being
inserted into the acupuncture point. This is followed by igniting the moxa and keeps it
burning (Fig. 1(b)). Typically, the distance between the skin surface and the burning moxa
stick is about 2 cm. Heat will be conducted from the needle handle to the needle itself and,
finally, to the surrounding tissues. This acupuncture design with a burning moxa can result
in a certain temperature gradient across the needle and enhances thus the Seebeck effect
(Cohen, 1997). In Chinese medicine theory, this method is highly recommended for use to
the patients with vacuity cold and wind damp (Wiseman, 1998) because of its functions of
warming the meridians and promoting the qi- and blood-flow. This therapy is also
applicable to release the cold-damp syndrome for the patients with rheumatoid arthritis
(Li, 1999). The other technique is called as the fire needle, which involves holding the needle
in a lamp flame until it becomes very hot. Afterwards, the needle is inserted to the
appropriate depth in the body quickly and it will be removed later on (Unschuld, 1988). In
comparison with the fire needle, the warming needle permits a longer retention and a
gentler heating.
In the present study, our aim is to study two types of the moxibustion effect, which are the
direct moxibustion and the warm needle moxibustion therapy. The acupoint GB 38 shown
in Fig. 2 is one of the acupoints in gall bladder (GB) meridian, which has an association with
the hemicrania and joint ache. Figure 3 shows the axial image of the right leg for the GB38

h
kT
t
ρ
∂
=∇⋅ ∇
∂
(1)

In the above equation, h
0
, k,
ρ
and T denote the internal energy, thermal conductivity,
density, and temperature, respectively.
Simulation of equation (1) will be carried out by employing the commercially available finite
volume package, namely, CFDRC (CFD-ACE-GUI, 2003). This software package provides
the modules CFD-GEOM for grid generation, CFD-ACE
+
for solution solver, and CFD-
VIEW for post-processing. A convenient graphical user interface (GUI) is also available for
us to specify the physical properties of the medium under investigation, and the
specification of the boundary and initial conditions. In CFD-ACE
+
solver, the finite volume
method employed together with the algebraic multigrid method and the conjugate gradient
squared solution solver accelerates calculation. In this study, the central difference scheme is
chosen to approximate the parabolic type partial differential equation.

GB38

(ThermaCAM® SC500 from FLIR Systems TM) (ThermaCAM SC500 Operator’s Manual),
which is equipped with a 45°close-up optic. Sensitivity, accuracy and resolution of the
employed camera are kept at 0.07 ºC, ± 2 ºC and 320 × 240 pixels, respectively. The distance
between the camera and the subject under current investigation is 0.1 m. The infrared
images of the subject obtained at a sampling rate of 4 Hz will be directly recorded in the
computer’s hard disk. calf
tibia
fibula
BC II
BC III
(T
E
=22
o
C)
BC I (T=37
o
C)
BC I (T=60
o
C)
BC II
GB 38
BC I: isothermal BC II: symmetry
BC III: external heat transfer (by convection)

Fig. 5. Schematic of the calf section around the acupoint GB 38 and the specified boundary

) is determined by balancing the heat fluxes between the environment
and the skin surface.
The heat transfer coefficient of the skin surface, specific heat and the density of tissues in the
investigated calf section are denoted as h
c
, Cp
c
and
ρ
c
, respectively. At the normal state, these
coefficients are prescribed respectively with h
c
= 3.7 W/m
2
ºC (Nishi and Gagge, 1970),
Cp
c
= 3,594 J/kgºC (Blake et al., 2000) and
ρ
c
= 1,035 kg/m
3
. The thermal conductivity of the
human tissues is assumed to change with the temperature (T) by the equation k
c
= 0.840419+
0.001403T W/mºC (Mura et al., 2006). The rest of the employed coefficients are tabulated in
the Table 1.


ρ
a

1.0 kg/m
3
Density of the air
h
s
7.9 W/m
2
ºC Heat transfer coefficient of the stainless steel
h
c
3.7 W/m
2
ºC Heat transfer coefficient of the calf
T
E
22 ºC Environment temperature
Table 1. Summary of the coefficients and the prescribed temperatures in the current
simulation
The predicted temperature on the skin surface is plotted in Fig. 6. The moxa temperature on
the skin surface is specified at 60 ºC (non-scarring direct moxibustion), which is the highest

Study of the Heat Transfer Effect in Moxibustion Practice

563
temperature that our skin can possibly endure, to avoid scarring. On the tibia and fibula,
their temperatures are given to be T= 37 ºC, which is the same as the normal human body
temperature. One can find from the upper and bottom planes of the simulated domain that

32
28
24
57
47
37
27

(a) (b)
Fig. 7. Comparison of the predicted and measured temperatures. (a) Measured by the IR
image recording system; (b) Predicted by the numerical simulation

Developments in Heat Transfer

564
A
B
heaven
man

earth 59
57
55
53
51
49
47

depths. Figure 8 (a) shows the temperature contours predicted at the plane of the acupoint
GB38 for the case that the moxa temperature on the skin surface is 60 ºC. From Fig. 8 (b), one
can see the predicted temperature profile along a line that is connected by two nodes A and
B. For the acupoints “heaven”, “man” and “earth”, they have three different depths at a
location in between the skin surface and the associated connective tissue. When the moxa
temperature is controlled at 60 ºC, which is the temperature considered in the case of non-
scarring moxibustion, the temperatures at the “heaven” (~ 0.5 cm beneath of the skin
surface), “man” (~ 1.0 cm beneath of the skin surface) and “earth” (~ 1.5 cm beneath of the
skin surface) are predicted as
60
heaven
T = 47.8 ºC,
60
man
T = 41.7 ºC and
60
earth
T = 39.0 ºC. From the
skin surface to “heaven”, we found that temperature decreases faster (12.2 ºC in between)
than those from the “heaven” to “man” (6.1 ºC in between) and from the “man” to “earth”
(2.7 ºC in between) as well because our body has a bigger thermal capacity than that of the
moxa. As a result, the temperature variation on the side of “heaven” is greater than that
along the “earth”. The relation between the predicted temperature (
T) and the depth (x) can
be expressed as

25283124155206
60 5.31 10 5 10 3 10 7 10 1 10 6 10Txxxxxx
−−−−−−
=− × +× −× +× −× +× (3)

67
87
107
T

(a) (b)
Fig. 9. (a) The predicted temperature contours on the cutting plane that passes through the
acupoint GB38 when the moxa temperature on the skin surface is 100 ºC; (b) The predicted
temperature profile along the line connected by two points
A and B shown in Fig. 9(a). The
“heaven”, “man” and “earth” represent three depths of the investigated acupoints,
respectively

A

B
heaven
man
earth

A
B
T
197
187
177
167
157
147
137

100
heaven
T
= 68.1ºC,
100
man
T = 51.3ºC and
100
earth
T
= 43.5ºC;
200
heaven
T
= 116.0ºC,
200
man
T
= 72.8ºC and
200
earth
T = 53.4º,
respectively. The predicted temperature contours on the plane of acupoint GB38 and the
temperature profile along the line connected by nodes
A and B are shown in Fig. 9 and
Fig. 10. The relation of the predicted temperature (T) and the depth (x) is expressed by the
equations given below

14283114155196
100 1.374 10 1 10 6 10 2 10 2 10 1 10Txxxxxx

structured- and unstructured-type meshes shown in Fig. 12, is generated from a total
number of 7,421 mesh points. The mesh density has been properly distributed so that the
predicted solutions can accurately represent the physical phenomenon. Fig. 12. The surface mesh points generated on the needle for acupuncture use

BC III
o
BC Ia (T=200
o
C)
GB38
GB38
tibia
calf
fibula
BC Ib (T=37
o
C)
BC II
needle

BC Ia: isothermal (T=200
o
C) BC Ib: isothermal (T=37
o
C)
BC II: symmetry BC III: external heat transfer (by convection)


27 º
C

133 º
C

27 ºC
133 ºC
needle
burning moxa

Fig. 14. Comparison of the numerically predicted and the experimentally measured
temperatures for the burning moxa stick applied on the handle of the acupuncture needle.
The temperature of burning moxa is 200 ºC. Temperature gradient will be established across
the needle, starting from the needle handle and ending at the needle head
In TCM, acupuncture needle can be made from stainless steel, iron, copper, silver and
pottery etc. For the safety and cost effectiveness reasons, stainless steel is now more popular.

Study of the Heat Transfer Effect in Moxibustion Practice

569
This study employs the normal stainless steel needle (1.5 inch needle, 7 cm total length with
3cm length in the needle handle part) in the experiment and numerical simulation. The
thermal conductivity, specific heat, density and heat transfer coefficient of the stainless steel
are denoted as
k
s
, Cp
s
,

warm needle moxibution. Around the skin surface of GB38 (Fig. 16), the surface temperature
near the needle is predicted to be about 36 ºC, which is 1 ºC higher than those predicted at
other skin surfaces (~ 35 ºC). Figure 17 shows the predicted temperature contours on the
cutting plane passing through the acupuncture needle and GB38 acupoint. The tissue
temperature around the needle is only 1 ºC higher than the others. Since the needle is
smaller in comparison with the human body, the effect of the burning moxa on the needle
handle is relatively less significant. In TCM, warm needle is involved in the acupuncture
with burning moxa. From Figs. 16 and 17, we can understand why this treatment isn’t called
as the hot needle, even the burning moxa can reach the temperature that is as high as 200 ºC.
Figure 18 shows the predicted temperature profile along the center line of the acupuncture
needle. From this profile, we can see that the temperature can be varied from 200 ºC
(burning moxa section) to 36 ºC (skin surface) in a short length of 2 cm. We can also observe
GB38

Developments in Heat Transfer

570
that the temperatures at locations beneath of the skin surface of depths 0 mm, 1 mm, 2 mm,
3 mm and 4 mm are 36.00 ºC, 35.63 ºC, 35.59 ºC, 35.62 ºC and 35.66 ºC, respectively. Fig. 16. The predicted skin surface temperature contours very near the acupoint GB38 Fig. 17. The predicted temperature contours on the cutting plane, which passes through the
acupoint GB38
depth 2 mm
GB38
needle
skin surface

surface have been also numerically predicted. In direct moxibustion, even for the lower
temperature treatment type (non-scaring type, moxa temperature equal to 60 ºC), human
tissue temperature is still increased by 12 ºC at the heaven position. This explains why
moxibustion rather than acupuncture has a better ability to treat severe diseases. In warm
needle moxibustion, along the centerline of the acupuncture needle the temperature
decreases very rapidly from the burning moxa section (200 ºC) to the skin surface (36 ºC).
The temperature near the needle is only 1 ºC higher than those predicted at other places.
This predicted phenomenon explains why we call it as the warm needle rather than as the
hot needle treatment. These results are fundamentally important in the study of TCM.
However, the physiological effect of warm needle moxibustion should include the
contributions of acupuncture. For this reason, a better understanding of the total effect of the
human body needs more intensive studies.
5. Acknowledgments
The financial support by the National Science Council under Grants NSC 97-2221-E-002-250-
MY3 is gratefully acknowledged. The authors also will acknowledge their thanks to Prof.
Ping-Hei Chen who kindly provided us the FLIR system to perform temperature
measurement.

Developments in Heat Transfer

572
6. References
[1] Blake, A. S. T., Petley, G. W., and Deakin, C. D., Effects of changes in packed cell volume
on the specific heat capacity of blood: implications for studies measuring heat
exchange in extracorporeal circuits. British Journal of Anaesthesia, 84(1), 2000, pp.
28-32.
[2] CFD-ACE-GUI User Manual Volume II. CFD Research Corporation, 2003, pp. 85-94.
[3] Chang, K. W., Meridian Anatomy. Zhi-Yang Press, 1999, pp. 47.
[4] Cohen, M., Kwok, G., and Cosic, I., Acupuncture needles and the Seebeck effect: do
temperature gradients produce electro-stimulation? Acupuncture and Electro -

Publications, Brookline, MA, 1998, pp. 664.
[19] Wu, M. X., Liu X. X., and Wu. B., The moxibustion influence of tendency in rehabilitation
for mouse osteoporosis fracture. Moderate Rehabilitation, 5(6), 2001, pp. 46-47.
[20] Yang, J. K., Meridian Cross-section Anatomy. Shang Hai Science Technology Press,
Chinese, 1997, pp. 76.
[21] Zhang, Q. W., Chinese Moxibustion Handbook. Tianjin, The Tianjin Press of Science
and Technology, 1993, pp. 1-5.
[22] Zhu, B., Scientific Foundations of Acupuncture and Moxibustion. Qingdao Press,
Qingdao, 1998.
29
Heat and Mass Transfer in
Jet Type Mold Cooling Pipe
Hideo Kawahara
Oshima National College of Maritime Technology
Japan
1. Introduction
Impinging jet is widely used in heating and cooling applications due to their excellent heat
transfer characteristics. To optimize heat transfer an understanding of the temperature field
as well as the velocity field is essential, in particular near the impingement surface where
the flow characteristics dominate the heat transfer process. Heat transfer distributions of jet
impingement and the effect of various geometric and flow parameters on heat transfer are
well documented, for example by Miranda & Campos (1999,2001), Kayansayan & Kucuka
(2001), Hrycak (1981), Gau & Chung (1991) and Lee et al. (1997).
Jet cooling pipes are used across a wide range of temperatures in die cooling, probes for
cryogenic surgery and other applications. Coolants are diverse, and range from liquid
nitrogen to water. In practice, these pipes are used especially with dies to improve quality,
by regulating die temperature and preventing sticking. Die cooling can be classified into
two basic types: straight-flow and jet. With the straight-flow type, lines for providing a flow
of cooling water are placed so as to follow the surface of the molded part, and this approach
is mainly used to uniformly cool the entire part. However, molded parts with a complex