Ch. 12 Two-dimensional imaging

Types of transducers and their characteristics

What transducer has a fixed focused and is NOT a phased array?

Mechanical transducer

How many crystals does a mechanical transducer have?

1 (disc-shaped)

Modern transducer arrays contain a single slab of PZT that are cut into a collection of separate pieces called ________. The combination of these with the wire and systems electronics is called _____.

elements; channel

What are the 5 types of phased arrays?

Linear phased array

Annular phased array

Linear sequential array

Convex sequential array (aka curved, curvilinear)

Vector array

What electrical technique does the beam use to steer and focus?

Phasing

What excites the crystals at different regions, creating slightly different electrical patterns?

Beam former

Which transducer experiences horizontal dropout with damaged PZT?

Annular phased array

Does the inner crystal in an annular phased array create the most shallow or a deeper part of the image?

Most shallow part of the image due to its smaller diameter.

Which transducer can be used in place of a vector array?

Linear sequential array due to its similar flat top of the probe

Which 3 transducers fire crystals simultaneously?

Linear sequential, convex sequential, and vector arrays

Which transducers experience vertical line dropout when PZT is damaged?

Linear sequential and curved sequential arrays

Which transducer is trapezoidal in shape?

Vector array (aka virtual sector)

Which two transducers have mechanical steering techniques?

Mechanical and annular phased arrays

We see slice thickness (aka elevational resolution) in ______ structures.

anechoic

Which transducers improve the slice thickness of a sound beam?

1.5-D arrays

Mechanical transducers

Annular phased arrays

True or false: The slice thickness focal zone is automatically adjusted when the sonographer adjusts the focal zone.

True

2D array transducers are electronically focused in both _____ and _____ planes

lateral and thickness

What technique imparts realism to a 3D image?

Rendering

What is the smallest component of a 3D image?

Voxel (aka volume element)

What lobe is created by a single element transducer?

Side lobes

What lobe is created by array transducers?

Grating lobes

What creates artifacts and degrades lateral resolution?

Side and grating lobes

What are the two techniques for fixing grating and side lobes?

1. Apodization (increase the strength of the signal in the center of the beam; decrease the strength on the outer edges of the beam)

2. Subdicing (divide crystal into groups of smaller crystals called sub-elements)

The 3D transmit hole and receive hole of a sound beam is also known as the _____.

dynamic aperture

What is the relationship between aperture size and lateral resolution?

Inversely related

True or false: Phased array always means “adjustable” or “multi-focus.”

True

Which of the following is an advantage of 1.5-D arrays?

reduced slice thickness

good axial resolution

ability to focus in the lateral plane

can make large images 

reduced slice thickness

With A-mode, the strength of the echo signal is represented by:

the height of the spike 

the brightness of the spike 

the brightness of the dot

the distance between two dots 

the distance between two spikes 

the height of the spike 

In m-mode, what axis is the time displayed?

x-axis

Which of the following is associated with a vector array?

mechanical steering

rectangular

azimuthal

expanded view

expanded view

The firing delay patterns of a linear phased array transducer________.

focuses the sound beam during transmission

improves temporal resolution

focuses the sound beam during reception

improves axial resolution

focuses the sound beam during transmission

Varying the excitation voltage to each crystal in the group used to form the ultrasound pulse is called ________.

interelement isolation 

subdicing 

dynamic aperture 

rectification

apodization

apodization

In B-mode, what axis is the amplitude displayed?

z-axis

In A-mode, the horizontal or x-axis represents reflector ____.

depth

Which of the following transducers creates a sector image shape?

all of the above 

annular array

phased array

linear sequential array

linear phased array and annular array 

linear phased array and annular array 

What is a typical value for the electrical signal delays in a convex phased array transducer?

10 ns

A machine that displays Doppler and two-dimensional images is called a ____ scanner.

duplex

True or false: The firing pattern that steers a beam left or right relates to the electronic curve. 

False (electronic slope)

True or false: Rendering creates an image from three-dimensional data acquired during the ultrasound exam.

True

An A-mode display is most commonly used for what type of ultrasound imaging?

opthalmology

In B-mode, which axis represents reflector depth?

x-axis

If you wish to use an array transducer that allows you to control transmit focal depth, what type would you select?

mechanical 

none of the above 

annular array

phased array

phased array

In B-mode, the brightness of the dot represents the ____.

amplitude

Which of the following transducers has the same line density in both the near and far fields?

curvilinear array

convex array

mechanical 

phased array

linear array

linear array

Which transducer is electronically focused but mechanically steered?

annular array

An M-mode display is most commonly used for what type of ultrasound imaging?

cardiac

The firing pattern that steers a beam to the left or right is called ______.

electronic slope

True or false: M-mode is used to access motion of cardiac walls and fetal heart motion in OB scans.

true

What information is present in the M-mode display?

a. time, motion pattern, and amplitude 

b. motion pattern, and amplitude 

c. bandwidth, amplitude, frequency, time and motion pattern

d. amplitude, frequency, and time

e. motion pattern, depth, and time

e. motion pattern, depth, and time

A M-mode display is associated with the following: (Choose all that apply)

dot is brightened by echo ampltiude

cross-sectional display (two spatial dimensions)

not a cross-sectional display

requires the beam to be scanned to develop the image

a depth versus time display

not a cross-sectional display

a depth versus time display

Which transducer creates a beam that is focused in all planes and all depths?

Annular phased array

focusing =

steering =

focusing = curvature

steering = slope

aka variable aperture

dynamic aperture

Compare 3D to 4D images

3D: static/still image

4D: real-time, moving picture

-Both need a 2D array transducer to work.