Ultrasound •(a) (b)
Ultrasound is a complete change X-ray and CT imaging ode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
ure 6.16 (a) B-mode image of a fetus. The dark region is the uterus, which is filled with fluid. (Courtesy of Professor M. H. Smet,
artment of Radiology) (b) B-m
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tricle), the two atria (LA left atrium; RA right atrium) and the origin of the aorta (outflow tract). Besides the anatomy of the whole heart, the rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
Figure6.17 B-modeimageacquisition can be done by either translating (a) or tilting (b) the transducer. (Courtesy of Professor J. D’hooge, Department of Cardiology. Reprinted with permission of Leuven University Press.)
•Object ansducer
modalities.
Similar to the principles of radar: uisitions. This is illustrated in Figu•re 6.17(a). This The same imaging modes are also used for sec-
transmit a pulse, then ‘listen’ for reflected waves.
d of imaging is called B-mode imaging, where B ond harmonic imaging. The difference with traditional nds for brightness (see also p. 14•0). If this mea- imaging is that the complete bandwidth of the trans- ement is repeated over time, an image sequence is ducer is not used during transmission but only a ained. low-frequency part. Higher harmonics are generated
Ultrasound, like sonar, uses sound waves. nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band-
Because bone has a high attenuation coefficient, during wave propagation and are detected with the
mple, the waves can approach the heart only ough the small space between the ribs. This space is en called the acoustic window. Because the acoustic
width of the transducer. The bandwidth used during transmission can be changed by modifying the prop- erties of the electrical pulses that excite the crystals.
dow for the heart is r•elatively small, the transla- n technique described above cannot be applied to
quent medical imaging modality (X-ray 1st)
Inexpensive
Excellent temporal resolution
Second most fre
diac applications. A possible solution is to scan a Image reconstruction Chapte
tor by tilting the transducer rather than translating Reconstructing ultrasound images based on the
see Figure 6.17(b)). acquired RF data as shown in Figure 6.14, involves
Non-invasive
Properties:
BMEN90021, Lecture set 5: Ultrasound
Transducer
Transducer
Other applications
ure6.16 (a)B-modeimage•ofafetus.Thedarkregionistheuterus,whichisfilledwithfluid.(CourtesyofProfessorM.H.Smet,
artment of Radiology) (b) B-mode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
Figure6.17 B-modeimageacquisition can be done by either translating (a) or tilting (b) the transducer. (Courtesy of Professor J. D’hooge, Department of Cardiology. Reprinted with permission of Leuven University Press.)
Non-destructive testing of materials to check for cracks
Ultrasound is not just a medical imaging technique.
tricle), the two atria (LA left atrium; RA right atrium) and the origin of the aorta (outflow tract). Besides the anatomy of the whole heart, the rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
uisitions. This is illustrated in Figure 6.17(a). This d of imaging is called B-mode imaging, where B nds for brightness (see also p. 140). If this mea- ement is repeated over time, an image sequence is
The same imaging modes are also used for sec- ond harmonic imaging. The difference with traditional imaging is that the complete bandwidth of the trans- ducer is not used during transmission but only a
ained. • low-frequency part. Higher harmonics are generated Because bone has a high attenuation coefficient, during wave propagation and are detected with the nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band-
dow for the heart is relatively small, the transla- n technique described above cannot be applied to
Sound navigation (SONAR) to locate fish or
mple, the waves can approach the heart only width of the transducer. The bandwidth used during
ough the small space between the ribs. This space is transmission can be changed by modifying the prop- en called the acoustic window. Because the acoustic erties of the electrical pulses that excite the crystals.
submarines
diac applications. A possible solution is to scan a Image reconstruction
tor by tilting the transducer rather than translating Reconstructing ultrasound images based on the
see Figure 6.17(b)).
Seismology to locate gas fields
acquired RF data as shown in Figure 6.14, involves
2 BMEN90021, Lecture set 5: Ultrasound
Transducer
Transducer
ansducer • Object
ansducer •
Figure6.17 B-modeimageacquisition can be done by either translating (a) or tilting (b) the transducer. (Courtesy of Professor J. D’hooge, Department of
History •(a) (b)
1877: The Theory of Sound (Rayleigh) rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
ure 6.16 (a) B-mode image of a fetus. The dark region is the uterus, which is filled with fluid. (Courtesy of Professor M. H. Smet,
artment of Radiology) (b) B-mode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
tricle), the two atria (LA left atrium; RA right atrium) and the origin of the aorta (outflow tract). Besides the anatomy of the whole heart, the
1880: Piezoelectric effect discovered ( )
submarines.
uisitions. This is illustrated in Figure 6.17(a). This The same imaging modes are also used for sec- d of imaging is called B-mode imaging, where B ond harmonic imaging. The difference with traditional
nds for brightness (see also p. 140).
ement is repeated over time, an image sequence is ducer is not used during transmission but only a ained. low-frequency part. Higher harmonics are generated Because bone has a h•igh attenuation coefficient, during wave propagation and are detected with the
en called the acoustic w
dow for the heart is relatively small, the transla-
n technique described above cannot be applied to
ging is th
Cardiology. Reprinted with permission of
Leuven University Press.)
During World War I, sonar used to detect
1942: Dussik brothers (Austrian) used ultrasound to indow. Because the acoustic erties of the electrical pulses that excite the crystals.
nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band-
mple, the waves can approach the heart only width of the transducer. The bandwidth used during
ough the small space between the ribs. This space is transmission can be changed by modifying the prop-
locate brain tumours
diac applications. A possible solution is to scan a Image reconstruction
tor by tilting the transducer rather than translating Reconstructing ultrasound images based on the
see Figure 6.17(b)).
1949: First pulse-echo experiment
1950: First 2-D image
1965: First 2-D real-time image (Siemens) 1968: Phased array technology
mid-1970’s: Electronic scanners
3 BMEN90021, Lecture set 5: Ultrasound
acquired RF data as shown in Figure 6.14, involves
Transducer
Transducer
Principles of Ultrasound
ure 6.16 (a) B-mode image of a fetus. The dark region is the uterus, which is filled with fluid. (Courtesy of Professor M. H. Smet,
artment of Radiology) (b) B-mode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
• A pulse of ultrasound is
tricle), the two atria (LA left atrium; RA right atrium) and the origin of the aorta (outflow tract). Besides the anatomy of the whole heart, the rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
emitted from a piezoelectric
transducer.
Figure6.17 B-modeimageacquisition can be done by either translating (a) or tilting (b) the transducer. (Courtesy of
Professor J. D’h
Leuven University Press.)
ooge, Depa
rtment Cardiology. Reprinted with permission of
• This pulse enters the body
uisitions. This is illustrated in Figure 6.17(a). This The same imaging modes are also used for sec-
d of imaging
nds for brightness (see also p. 140). If this mea- imaging is that the complete bandwidth of the trans-
ic imaging
and is partially reflected from
ement is repeated over time, an image sequence is ducer is not used during transmission but only a
ained. low-frequency part. Higher harmonics are generated
Because bone has a high attenuation coefficient, during wave propagation and are detected with the
nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band- mple, the waves can approach the heart only width of the transducer. The bandwidth used during ough the small space between the ribs. This space is transmission can be changed by modifying the prop-
en called the acoustic window. Because the acoustic erties of the electrical pulses that excite the crystals.
internal surfaces boundaries
dow for the heart is relatively small, the transla- n technique described above cannot be applied to
see Figure 6.17(b)).
• Those reflected waves that travel exactly back along the incident wave direction are detected by the receiver.
cally different tissues.
diac applications. A possible solution is to scan a Image reconstruction
tor by tilting the transducer rather than translating Reconstructing ultrasound images
4 BMEN90021, Lecture set 5: Ultrasound
Transducer
Transducer
Principles of Ultrasound
ure 6.16 (a) B-mode image of a fetus. The dark region is the uterus, which is filled with fluid. (Courtesy of Professor M. H. Smet,
artment of Radiology) (b) B-mode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
• Sound imaging:
tricle), the two atria (LA left atrium; RA right atrium) and the origin of the aorta (outflow tract). Besides the anatomy of the whole heart, the rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
Figure6.17 B-modeimageacquisition can be done by either translating (a) or tilting (b) the transducer. (Courtesy of Professor J. D’hooge, Department of Cardiology. Reprinted with permission of Leuven University Press.)
• Measuring the elapsed time between the emission of a sound pulse and the reception of an echo from an
internal body boundary.
ement is repeated over time, an image sequence is ducer is not used during transmission but only a
uisitions. This is illustrated in Figure 6.17(a). This The same imaging modes are also used for sec- d of imaging is called B-mode imaging, where B ond harmonic imaging. The difference with traditional
nds for brightness (see also p. 140). If this mea- imaging is that the complete bandwidth of the trans-
ained. low-frequency part. Higher harmonics are generated
• The various organs have different mechanical tissue
dow for the heart is relatively small, the transla-
• At boundaries sound waves are scattered and the resulting echoes travel back to the receiver to form an image.
• Sound emitted or reflected from moving object suffers a change in frequency Doppler effect (Doppler ultrasound imaging).
Because bone has a high attenuation coefficient, during wave propagation and are detected with the
nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band-
mple, the waves can approach the heart only width of the transducer. The bandwidth used during
ough the small space between the ribs. This space is transmission can be changed by modifying the prop- en called the acoustic window. Because the acoustic erties of the electrical pulses that excite the crystals.
n technique described above cannot be applied to
properties, which lead to change in sound velocity.
diac applications. A possible solution is to scan a Image reconstruction
tor by tilting the transducer rather than translating Reconstructing ultrasound images based on the see Figure 6.17(b)). acquired RF data as shown in Figure 6.14, involves
5 BMEN90021, Lecture set 5: Ultrasound
Transducer
Transducer
boundary between tissue types.
Basic principles
c2 = l2.f incident
wavefront c1
ure6.16 (a)B-modeimage•ofafetus.Thedarkregionistheuterus,whichisfilledwithfluid.(CourtesyofProfessorM.H.Smet, partment of Radiology) (b) B-mode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
These reflections measured as functions of time.
quisitions. This is illustrated in Figu•
re 6.17(a). This The same imaging modes are also used for sec-
nd of imaging is called B-mode imaging, where B ond harmonic imaging. The difference with traditional
nds for brightness (see also p. 140). If this mea- imaging is that the complete bandwidth of the trans-
Leuven University Press.)
Cardiology. Reprinted with permission of
Figure 6.8 Schematic representation of reflection of an incident
reflected wavefront
A propagating acoustic wave partially reflects at the
tricle), the two atria (LA left atrium; RA right atrium) and the origin of the aorta (outflow tract). Besides the anatomy of the whole heart, the rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
Figure6.17 B-modeimageacquisition can be done by either translating (a) or tilting (b) the transducer. (Courtesy of Professor J. D’hooge, Department of
Transducer
wave at a planar interface of two different media. The relationships
Transducer
between the angles θi is given in Eq. (6.15).
If velocity in tissue is known, position can be inferred
rement is repeated over time, an image sequence is ducer is not used during transmission but only a
ample, the waves can approach the heart only rough the small space between the ribs. This space is en called the acoustic window. Because the acoustic
width of the transducer. The bandwidth used during transmission can be changed by modifying the prop- erties of the electrical pulses that excite the crystals.
c1 = l1. f c2 = l2. f
incident wavefront
from measured reflections.
tained. low-frequency part. Higher harmonics are generated
Because bone has a high attenuation coefficient, during wave propagation and are detected with the
nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band-
refracted wavefront
ndow for the heart is r• Other effects:
elatively small, the transla- n technique described above cannot be applied to
rdiac applications. A possible solution is to scan a Image reconstruction
ctor by tilting the transducer rather than translating Reconstructing ultrasound images based on the
see Figure 6.17(b)).
acquired RF data as shown in Figure 6.14, involves
hematic repre•
diffraction
s in this figure •
sentation of Huygens’ principle. The
represent the wavefronts, i.e., surfaces es have the same phrase.fArnay pcotiniot on a wavefront
red as the sou•
rce of secondary waves and the
t to these secondary waves determines the future
wavefront. •
attenuation
dispersion
is a surface•where the waves have the same
BMEN90021, Lecture set 5: Ultrasound
Figure 6.9 Schematic representation of refraction of an incident
tricle), the two atria (LA left atrium; RA right atriu
tilting (b) the transducer. (Courtesy of Professor J. D’hooge, Department of Cardiology. Reprinted with permission of Leuven University Press.)
Ultrasound physics
Ultrasound waves are longitudinal compression rphology of the valves (e.g., mitral valve) can be visualized. (Courtesy of the Department of Cardiology.)
ure 6.16 (a) B-mode image of a fetus. The dark region is the uterus, which is filled with fluid. (Courtesy of Professor M. H. Smet,
artment of Radiology) (b) B-mode image of a normal heart in a four-chamber view showing the two ventricles (LV left ventricle; RV right
m) and the
wavesFigure 6.17 B-mode image acquisition can be done by either translating (a) or
ct). Besid
f the whole h
Direction of particles is parallel to direction of wave motion.
uisitions. This is illustrated in Figu•re 6.17(a). This The same imaging modes are also used for sec- d of imaging is called B-mode imaging, where B ond harmonic imaging. The difference with traditional nds for brightness (see also p. 140). If this mea- imaging is that the complete bandwidth of the trans- ement is repeated over time, an image sequence is ducer is not used during transmission but only a
Because bone has a high attenuation coefficient, dur
Regions of high & low particle density are generated by
mple, the waves can approach the heart only width of the transducer. The bandwidth used during
nsmission of sound through bone is minimal. For remaining high-frequency part of the sensitive band-
ough the small space between the ribs. This space is
low-frequency part. Higher harmonics are generated
ement of particles.
Compression and rarefaction acquired RF data as shown in Figure 6.14, involves
cal displac
Chapter 6: Ult
Figure6.1 Sch wave can be repr connected by m displaced from t (From T.G. Press, permission of Ac
en called the acoustic window. Because the acoustic erties of the electrical pulses that excite the crystals.
dow for the heart is relatively sm•all, the transla- n technique described above cannot be applied to
diac applications. A possible solution is to scan a Image reconstruction
tor by tilting the transducer rather than translating Reconstructing ultrasound images based on the
see Figure 6.17(b)).
7 BMEN90021, Lecture set 5: Ultrasound Table6.1 Valuesoftheacousticw
a consequence of these phenomena, the compression
Transducer
Transducer
uisitions. This is illustrated in Figure 6.17(a). This d of imaging is called B-mode imaging, where B nds for brightness (see also p. 140). If this mea-
mple, the waves can approach the heart only ough the small space between the ribs. This space is en called the acoustic window. Becau•se the acoustic
dow for the heart is relatively small, the transla- n technique described above cannot be applied to diac applications. A possible solution is to scan a tor by tilting the transducer rather than translating
width of the transducer. The bandwidth used during transmission can be changed by modifying the prop- erties of the electrical pulses that excite the crystals.
see Figure 6.17(b)).
Frequency of wave is within audible range for humans, 20 Hz – 20 kHz.
ement is repeated over t•ime, an image sequence is ducer is not used during transmission but only a ained. low-frequency part. Higher harmonics are generated Because bone has a high attenuation coefficient, during wave propagation and are detected with the
Why “ultra”sound?
ure 6.16 (a) B-mode image of a fetus. The dark region is the uterus, which is filled with fluid. (Courtesy of Professor M. H. Smet,
• Soundwavesarecharacterisedbywavelength𝜆and
artment of Radiol
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