Biomedical Engineering Reference
In-Depth Information
equation given in the chapter. On the same graph, plot the temperature, ignoring the effect of
conduction, which assumes linear variation with time. Comment on your findings in relation
to the diffusion time found in problem 7.
15.
Consider skin tissue that is exposed to linear heating—for example, as in pulsed laser
coagulation—such that
T
o
is the initial temperature (e.g., 37
C) and m is
the rate of heating (e.g., 10
3
C/s). Describe how you would find the critical temperature for
thermal damage. Do you expect that to be lower or higher than the constant temperature case
of the same exposure duration?
16.
For the study of ablation onset time, plot A graph of B
T
¼
T
o
þ
mt, when
p
t
ab
versus Bl. Measure the slope for
; it should be
2
“large” values of
p . For absorption coefficient 100/cm and a laser intensity
1,000 W/cm
2
, find the time for the onset of ablation using water thermal properties, assuming
ablation initiates at 150
C.
B
l
17.
In the visible optical region, tissue scattering dominates absorption. Assume that the
scattering coefficient of a 5-cm-thick tissue is 100 cm
-1
and the wavelength of light is 0.5
m.
In order to detect on average a single ballistic photon transmitted through the tissue, what is
the energy in Joules that is required for the incident light? Compare the energy of the incident
light with the rest energy of the earth using Einstein's mass-energy equivalence equation
E
¼
mc
m
10
24
kg.
18.
Use the diffusion theory to estimate light penetration in biological tissues. A 10 mW isotropic
point source is buried in an infinite turbid medium. Assume that the absorption coefficient is
0.1 cm
1
, the scattering coefficient of a 5-cm-thick tissue is 100 cm
1
, the scattering anisotropy is
0.9, and the wavelength of light is 0.5
2
, where the mass of the earth is 6
m. Calculate the light fluence rate 5 cm from the source.
19.
Use diffusion theory to estimate sonoluminescence light transmission in biological tissues.
A 1 mW isotropic point source is buried in an infinite turbid medium. Assume that the
absorption coefficient is 0.1 cm
1
, the scattering coefficient is 100 cm
1
, and the scattering
anisotropy is 0.9. Calculate the light fluence rate integrated over a sphere of a 5 cm radius
centered at the source.
20.
What additional information does the phase measurement in a frequency-domain imaging
technique provide compared with the continuous wave technique that measures only the
amplitude of the diffuse light?
m
Suggested Readings
G. Boisd´, A. Harmer, Chemical and Biochemical Sensing with Optical Fibers and Waveguides, Artech House,
Boston and London, 1996.
M. Born, E. Wolf, Principles of Optics, seventh expanded ed., Cambridge University Press, 1999.
B. Culshaw, J. Dakin, Optical Fiber Sensors: Vols. I and II, Artech House, Boston and London, 1989.
F.A. Duck, Physical Properties of Tissue, Academic, London, 1990.
E. Hecht, Optics, Addison-Wesley, Reading, MA, 1987.
A. Katzir, Lasers and Optical Fibers in Medicine, Academic Press Inc., San Diego, CA, 1993.
J. Lakowicz, Principles of Fluorescence Spectroscopy, second ed., Kluwer Academic/Plenum Publishers, 1999.
F.L. Pedrotti, L.S. Pedrotti, Introduction to Optics, second ed., Prentice Hall, Upper Saddle River, NJ, 1993.
V. Tuchin, Tissue Optics: Light Scattering Methods and Instruments for Medical Diagnosis, Society of Photo-
Optical Instrumentation Engineers Press, Bellingham, Washington, 2000.
