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Chapter 1: Principles of Two-Dimensional and Three-Dimensional Ultrasound

This chapter introduces the core physics and operation of ultrasound machines, with a focus on 2D and 3D imaging. The fundamentals of sound wave generation and transducer technology are presented. Illustrative diagrams and video demonstrations will support readers in understanding ultrasound principles and image formation.

1

Figures

Transmitting power and indices. ME 4C (A–C) and ME long-axis color Doppler (D–F) views show (A, D) transmitting power in decibels (dB). A value of 0 dB specifies the emitting source is at 100% of its power. (B, E) Reduced transmitting power results in negative dB, and both the mechanical index (Ml) and the soft tissue thermal index (TIS) decrease.<em> Abbreviations</em>: 4C, four chamber; Ao, aorta; LA, left atrium; LV, left ventricle; ME, mid-esophageal; RA, right atrium; RV, right ventricle. <i class='fa fa-video-camera' aria-hidden='true'></i></p>

eFigure 1.3

Transmitting power and indices. ME 4C (A–C) and ME long-axis color Doppler (D–F) views show (A, D) transmitting power in decibels (dB). A value of 0 dB specifies the emitting source is at 100% of its power. (B, E) Reduced transmitting power results in negative dB, and both the mechanical index (Ml) and the soft tissue thermal index (TIS) decrease. Abbreviations: 4C, four chamber; Ao, aorta; LA, left atrium; LV, left ventricle; ME, mid-esophageal; RA, right atrium; RV, right ventricle.

3D image displays. Conventional 3D rendering uses shading techniques to encode voxels based on their distance, grey-level gradient, and texture to generate a display of cardiac structures in 3D. Computer-generated lighting uses shadowing, transparency and opacity effects to create the depth perception. Shown is a 3D dataset of a mitral valve P2 prolapse on a 2D display using different options, such as (A) standard mode, (B) TrueVue® (Philips, Andover, MA) and (C) TrueVue Glass® (Philips, Andover, MA).<em> Abbreviations</em>: 2D, two-dimensional; 3D, three-dimensional <i class='fa fa-video-camera' aria-hidden='true'></i></p>

eFigure 1.13

3D image displays. Conventional 3D rendering uses shading techniques to encode voxels based on their distance, grey-level gradient, and texture to generate a display of cardiac structures in 3D. Computer-generated lighting uses shadowing, transparency and opacity effects to create the depth perception. Shown is a 3D dataset of a mitral valve P2 prolapse on a 2D display using different options, such as (A) standard mode, (B) TrueVue® (Philips, Andover, MA) and (C) TrueVue Glass® (Philips, Andover, MA). Abbreviations: 2D, two-dimensional; 3D, three-dimensional

Multi-slice image display. The multi-slice display option cuts a 3D dataset to show multiple 2D images on a single display. Shown is a full volume 3D dataset from a ME 4C view with reconstruction of 2D SAX views at multiple levels. This display option allows the rapid evaluation of RWMA as after coronary revascularisation.<em> Abbreviations</em>: 2D, two-dimensional; 3D, three-dimensional; 4C, four-chamber; ME, mid-esophageal; RWMA, regional wall motion abnormalities; SAX, short-axis. <i class='fa fa-video-camera' aria-hidden='true'></i></p>

eFigure 1.14

Multi-slice image display. The multi-slice display option cuts a 3D dataset to show multiple 2D images on a single display. Shown is a full volume 3D dataset from a ME 4C view with reconstruction of 2D SAX views at multiple levels. This display option allows the rapid evaluation of RWMA as after coronary revascularisation. Abbreviations: 2D, two-dimensional; 3D, three-dimensional; 4C, four-chamber; ME, mid-esophageal; RWMA, regional wall motion abnormalities; SAX, short-axis.

Overall gain control. (A-C) ME AoV short-axis view showing the effect of varying gain on the visual quality of the image by comparing (A) the gain of 70% with (B) the lower gain of 33%. (D) Relationship between brightness and AoV echogenicity, which represents the strength of the reflected signal from a given location in the patient. Higher gain value means that weaker signals (left of the x-axis) are given a high brightness. With a gain of 70%, the signal of most of the AoV is saturated (white), while a gain of 33% offers more contrast, the slope being located horizontally within the AoV echogenicity range in the image as represented by the figure. Echo signals below the chosen minimal threshold will appear as black pixels, while those exceeding the maximal range will appear uniformly as dense white pixels. Adjusting total gain changes the position of the center of the slope relative to the available range enhancing brightness within that range.<em> Abbreviations</em>: AoV, aortic valve; LA, left atrium; ME, mid- esophageal; RA, right atrium. <i class='fa fa-video-camera' aria-hidden='true'></i></p>

eFigure 1.16

Overall gain control. (A-C) ME AoV short-axis view showing the effect of varying gain on the visual quality of the image by comparing (A) the gain of 70% with (B) the lower gain of 33%. (D) Relationship between brightness and AoV echogenicity, which represents the strength of the reflected signal from a given location in the patient. Higher gain value means that weaker signals (left of the x-axis) are given a high brightness. With a gain of 70%, the signal of most of the AoV is saturated (white), while a gain of 33% offers more contrast, the slope being located horizontally within the AoV echogenicity range in the image as represented by the figure. Echo signals below the chosen minimal threshold will appear as black pixels, while those exceeding the maximal range will appear uniformly as dense white pixels. Adjusting total gain changes the position of the center of the slope relative to the available range enhancing brightness within that range. Abbreviations: AoV, aortic valve; LA, left atrium; ME, mid- esophageal; RA, right atrium.

Dynamic range compression. (A-C) ME AoV short-axis views show the effect of varying compression adjustments on the visual quality of the image by comparing (A) the compression of 30 with (B) the higher compression at 60. (D) Any echogenicity (x axis) value smaller than the value of the foot of the slope, or greater than the value under the top of the slope will not be visualized as they will appear black or white, respectively. However, all image areas that have an echogenicity value that fall directly under the slope on the x axis are adequately visualized, as they have a different brightness (y axis) value than other image areas of different echogenicity. Therefore, a dynamic range compression of 30 corresponds to a narrower range of echogenicity being adequately visualized, while a value of 60 will allow for a wider range of echogenicity being adequately visualized. These settings correspond to a narrower and a wider dynamic range,<em> Abbreviations</em>: AoV, aortic valve; LA, left atrium; ME, mid-esophageal. RA, right atrium. <i class='fa fa-video-camera' aria-hidden='true'></i></p>

eFigure 1.17

Dynamic range compression. (A-C) ME AoV short-axis views show the effect of varying compression adjustments on the visual quality of the image by comparing (A) the compression of 30 with (B) the higher compression at 60. (D) Any echogenicity (x axis) value smaller than the value of the foot of the slope, or greater than the value under the top of the slope will not be visualized as they will appear black or white, respectively. However, all image areas that have an echogenicity value that fall directly under the slope on the x axis are adequately visualized, as they have a different brightness (y axis) value than other image areas of different echogenicity. Therefore, a dynamic range compression of 30 corresponds to a narrower range of echogenicity being adequately visualized, while a value of 60 will allow for a wider range of echogenicity being adequately visualized. These settings correspond to a narrower and a wider dynamic range, Abbreviations: AoV, aortic valve; LA, left atrium; ME, mid-esophageal. RA, right atrium.

Persistence. (A–C) Digital post-processing can substantially affect the image appearance of these ME AoV SAX views. Persistence (P) defines how much of the previous image appears in the current frame. The averaging of successive frames reduces the variations in the image between frames, so the image appears smoother (C) but with lower temporal resolution. The frame rate at 64 HZ is not altered.<em> Abbreviations</em>: AoV, aortic valve; C, compression; Gen, general; LA, left atrium; ME, mid-esophageal; RA, right atrium; SAX, short-axis.<i class='fa fa-video-camera' aria-hidden='true'></i></p>

eFigure 1.21

Persistence. (A–C) Digital post-processing can substantially affect the image appearance of these ME AoV SAX views. Persistence (P) defines how much of the previous image appears in the current frame. The averaging of successive frames reduces the variations in the image between frames, so the image appears smoother (C) but with lower temporal resolution. The frame rate at 64 HZ is not altered. Abbreviations: AoV, aortic valve; C, compression; Gen, general; LA, left atrium; ME, mid-esophageal; RA, right atrium; SAX, short-axis.

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Videos

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Chapter 01 Fig10A

Chapter 01 Fig10B

Chapter 01 Fig11

Chapter 01 Fig12A

Chapter 01 Fig12D

Chapter 01 Fig13A

Chapter 01 Fig13B

Chapter 01 Fig13C

Chapter 01 Fig14

Chapter 01 Fig15ABDE

Chapter 01 Fig16A

Chapter 01 Fig16B

Chapter 01 Fig17A

Chapter 01 Fig17B

Chapter 01 Fig19A

Chapter 01 Fig19B

Chapter 01 Fig19C

Chapter 01 Fig20A

Chapter 01 Fig20C

Chapter 01 Fig21A

Chapter 01 Fig21C

3

Tables

eTable 1.1 Parameters for describing waves

Parameters

Symbol

Basic units

Units

Mainly determined by

Amplitude

A

Pressure or density

N/m2, Pa or g/cm3

Source and medium

Frequency

f

1/Time

Hz, MHz, sec–1

Sound source

Intensity

I

Power/area

W/m2

Sound source

Period

τ

Time

sec, μsec

Sound source

Power

P

Work/time

J/sec, W

Sound source

Pressure

P

Force/area

N/m2, Pa

Source and medium

Propagation speed

c

Distance/time

m/sec

Medium

Wavelength

λ

Distance

m, cm, mm

Source and medium

eTable 1.2 Ultrasound properties of common materials

Material

Density (g/cm3)

c
(m/sec)

Z
(rayls × 10–5)

Attenuation Coefficient
(dB/cm at 1 MHz)

Air

0.0000012

331

0.0004

12

Fat

0.95

1450

1.38

0.63

Muscle

1.1

1580

1.70

0.5–1.0

Skull bone

1.91

4080

7.80

20

Abbreviations: c, speed of sound; dB, decibel; Z, acoustic impedance, which is the product of density and speed of sound.

eTable 1.3 Relative ultrasound intensity changes for decibel (dB) values

dB

Relative Intensity

–40

0.0001

–30

0.001

–20

0.01

–10

0.1

–3

0.5

–2

0.63

–1

0.79

0

1.0

Note that a reduction of –10 dB and –3 dB means that a reduced intensity by one-tenth and one-half, respectively.

eTable 1.4 Parameters describing pulsed ultrasound

Parameters

Basic units

Units

Determined by

Common values

Pulse repetition period

Time

sec, ms, μsec

Sound source

0.1–1.0 ms

Pulse repetition frequency

1/Time

sec–1, Hz

Sound source

1–10 kHz

Pulse duration

Time

sec, ms, μsec

Sound source

0.5–3.0 μsec

Duty factor

None

None

Sound source

0.001–0.01

Spatial pulse length

Distance

mm, cm

Source and medium

0.1–1.0 mm