Biomedical Engineering Reference
In-Depth Information
If the liquid travels at the same speed as the blood, what frequency would
be measured as a result of the Doppler shift?
(c) Explain in one or two sentences why it is difficult to scan objects located behind
bone using ultrasound.
8.6
Derive an equation for Compton scattering using the conservation of energy
and momentum principles.
8.7
We are interested in using a 30-keV energy source. The goal is to separate the
view of lungs from the ribcage. The thickness of the bone is 2 cm and lung
thickness is 10 cm. What are the differences in the transmitted energies.
8.8
A tissue containing bone and adipose tissue of equal thickness (8 cm) are ex-
posed to a 15-keV X-ray. What is the expected difference in energy at 8 cm?
8.9
We are using a 50-keV X-ray source for the imaging bone. If the emitted X-ray
is 38 keV, what is the effective thickness of the bone?
8.10
A primary solar cosmic ray proton travels 1 km in the atmosphere. If its ki-
netic energy is 2 GeV, what is its LET value in air?
8.11
Calculate the LET rate for the following cases:
(a) A 600-eV electron gives up its energy in water within a distance of 109
nm.
(b) A 800-keV proton gives up its energy in water within a distance of
17.7
μ
m.
(c) A 5.3-MeV alpha particle gives up its energy in water within a distance of
0.482 mm.
8.12
A 100-MeV fission fragment gives up its energy in water within a distance of
1.11
10
−5
m. Calculate its LET rate.
×
8.13
If the ionizing potential of a hydrogen atom is 10.6 eV, how may ionizations
will be created by an absorbed alpha particle if its incident kinetic energy of
100 MeV is totally absorbed? 9.4
10
4
×
A general rule of thumb used by physicists is that about 30 eV is needed
for each ionization in liquid water, whereby H
2
O is broken into H
+
and OH
−
.
How many ionizations are created in water by a single 800-keV proton?
8.14
How many ionizations are created in water by a single 2-GeV proton?
8.15
The electric field associated with a plane EM wave is given by
E
x
=
0,
E
y
=
10
−4
V/m and
k
10
6
m
−1
.The
0,
E
z
=
E
0
sin
k
(
x-ct
) where
E
0
=
2.34
×
=
9.72
×
wave is propagating in the
x
direction. Write expressions for the components
of the magnetic field of the wave. Find the wavelength of the wave.
+
8.16
The intensity of direct solar radiation not absorbed by the atmosphere on a
particular summer day is 130 W/m
2
. How close would you have to stand to a
1.0-kW electric heater to feel the same intensity? Assume that the heater radi-
ates uniformly in all directions.
8.17
The maximum electric field at a distance of 11.2m from a point light source is
1.96 V/m. Calculate: (a) the amplitude of the magnetic field; (b) the intensity;
and (c) the power output of the source.
