Recommended Ultrasound Terminology

Figures

Figure 1

Standard body planes in ultrasound imaging, indicated by the plane perpendicular to the plane of this page and passing through the line A–B.

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Figure 2

Definitions for focusing measurements when the transducer geometry is unknown ultrasonic transducer.

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Figure 3

Top, Field parameters for a nonfocusing transducer. Bottom, Field parameters for a focusing transducers.

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Figure 4

Beam contour (–6, –12, and –20 dB) for a 5-MHz curved transducer centered at location 0,0 (bottom center of graph) with a diameter of 25 mm and a radius of curvature of 50 mm.

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Figure 5

Parameters for describing a focusing transducer of a known geometry. Figure 5 wo caption

Figure 6

Reflection and refraction at a boundary between two media.

Figure 7

Beamwidth focus in a principal longitudinal plane. Top, For a transducer of known geometry. Bottom, for a transducer of unknown geometry (measurement case).

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Figure 8

Types of geometric focusing. Top, Geometric line focus. Bottom, Geometric spherical focus.

Figure 9

Pressure focus in a principal longitudinal plane. Top, For a transducer of known geometry. Bottom, for a transducer of unknown geometry (measurement case).

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Figure 10

Beam patterns of single-element and multielement transducers showing side lobes and grating lobes.

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Figure 11

Half wave and full wave rectification.

Figure 12

Temporal-peak and temporal-average intensities.

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Figure 13

Voltage overshoot.

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Figure 14

Beam plot showing side lobes, plotted in decibels versus angle. Shown are the main lobe centered at 0°, and at either side of the main lobe are the side lobes.

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Figure 15

Acoustic enhancement seen distal to a low attenuating structure.

Figure 16

Acoustic shadow seen distal to a high-attenuating structure.

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Figure 17

Anechoic regions in fluid-filled structures.

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Figure 18

Annular transducer arrays. Note elements are in the form of concentric rings that are shaped like a bull’s eye target.

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Figure 19

Linear transducer arrays. The top shows a curved linear array and its image format. The bottom shows an ordinary (straight) linear array and its image format, which is rectangular. Within the rectangle is a parallelogram-shaped inset commonly used for color flow or Doppler imaging. Note that phased arrays look physically like linear arrays but scan in an angle from a central point in the array and have a sector-shaped format exemplified by Figures 21 and 29.

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Figure 20

Effect of damping on transmitted pulse length. Shortening the transmitted pulse length produces better axial resolution. Better damping can be obtained by either a thicker backing or by increasing the absorption and scattering within the backing material.

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Figure 21

Mirror image artifact. Here the diaphragm acts as an acoustic mirror and maps a duplicate image of the region above it to the region below and here, to the left of the diaphragm. It is an artifact because structures appear at deeper depths where they don't exist.

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Figure 22

Refraction edge shadows.

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Figure 23

Multiple comet tail artifacts (reverberations).

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Figure 24

Artifactual twin resulting from refraction through the rectus muscle.

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Figure 25

Full width half maximum widths of beams in a focal plane from either a line aperture or a circular aperture. Scaling adjusted so a square aperture (a line aperture on a side) and a circular aperture have the same area.

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Figure 26

Envelope of a waveform. The envelope and quadrature (complex imaginary) signal are derived from the real signal. The real and quadrature signals are part of a complex analytic signal.

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Figure 27

Coordinate system showing the relationship among the elevation and azimuthal (scan ) planes and a linear array with array elements. A transmit scan line is formed by an active aperture, a group of elements excited at the same time. As an active aperture moves along the length of the aperture, the emitted scan line moves with it.

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Figure 28

A typical pair of A-lines before (solid line) and after (dashed line) compression.

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Figure 29

Diagram of a sector transducer (left) shows successive lines of propagation sweeping from left to right and numbered 1 through 128. The sector shape of the image on the display is shown on the right.

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Figure 30

Convex array with scan lines and corresponding B-mode image.

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Figure 31

(top) Repeated pressure waveforms vs time. (middle) Pulsed intensity vs time. (bottom), intensity waveform maximum is temporal peak (TP) vs time and average intensity is the temporal average (TA) intensity over time.

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Figure 32

Peak compressional (pc) and peak rarefactional (pr) pressures depicted on a pressure waveform vs time.

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Figure 33

Diagram shows variation in elevational slice width with depth. Pulses propagate downward from the linear array within the slice depicted below the array. Elevational resolution is best where the slice width is minimum.

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Figure 34

The summing of the amplitudes of acoustic scan lines of the linear array steered in different directions (here three are shown) produces a spatially compounded image with less speckle.

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Figure 35

Steered wavefront from a phased array.

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Figure 36

Transducer with an acoustic lens built into the transducer face (the ridge is shown between the arrows). This lens is used to focus the beam in the elevation plane. See Figure 33.