Chapter 12

Question 1

Mechanical Transducer

Answer 1

Not in use today
Contains a single, circular, disc shaped element
image is sector (fan or pie) shaped
small footprint
Focusing was mechanical
Crystal damage lost entire image

Question 2

Footprint

Answer 2

face of probe that comes into contact with the skin

Question 3

a channel

Answer 3

Each element is connected by a wire to its own electronic circuitry

Question 4

Arrays

Answer 4

contain multiple active elements
A single slab of PZT is cut into many pieces or elements

Question 5

Array Transducers

Answer 5

Linear: Active elements are arranged in a straight line
Annular: Elements are arranged as circular rings of PZT
Convex, Curved or Curvilinear: Elements are arranged in a curved, bowed, or arched line

Question 6

Linear Phased Array Transducer (cardiac sector probes)

Answer 6

Compact with small (~1 cm) rectangular footprint;
Elements are very thin
100-300 narrow rectangular elements
beam is focused electronically

Question 7

phasing

Answer 7

All crystals are stimulated to create each beam

Question 8

Linear Phased Array and Multi-focusing

Answer 8

To create an image with multiple foci at different depths, the system must send multiple sound beams down each scan line

Question 9

Dynamic Receive Focusing

Answer 9

A more accurate image can be created when the ultrasound receiver introduces time delays to some of the electrical signals during reception
(performed automatically)

Question 10

Annular Phased Array Transducer

Answer 10

Elements are rings of PZT
Mechanical steering
Small footprint
Fan or pie shaped
Electronic focusing
Horizontal band of dropout

Question 11

Linear Sequential Array Transducer

Answer 11

Large footprint
rectangular image
Used in vascular imaging
120-250 strips of PZT
Electronic steering
vertical band of dropout

Question 12

sequencing

Answer 12

Elements are stimulated in groups simultaneously to send the pulse straight ahead
Then the next group of crystals is stimulated to direct the next sound beam straight ahead

Question 13

Convex, Curved, or Curvilinear Sequential Array Transducers

Answer 13

120-250 strips of PZT
used for Abdominal or OBGYn
Large footprint
beams steered electronically with sequencing
top of sector wide as footprint
electronically focused
vertical band of dropout

Question 14

Vector Array Transducers

Answer 14

120-250 strips of PZT
medium footprint
beam steering electronically sequenced
electronic focusing
vertical band of dropout
trapezoid image
vascular and cardiac image

Question 15

Image resolution

Answer 15

Shallow to deep = longitudinal resolution
Side to side = lateral resolution
Top to bottom (height) of the imaging plane = slice thickness/elevational resolution

Question 16

Ranking of resolutions for disc probes from best to worst

Answer 16

longitudinal then lateral/elevational

Question 17

Ranking for these 1D array probes

Answer 17

longitudinal/axial resolution is best, then lateral, then elevational

Question 18

ranking with 1 1/2 probes

Answer 18

axial, lateral, then elevational

Question 19

Three-Dimensional (volume) Imaging

Answer 19

Utilizes a 2D array (as many rows as columns)
Thousands of elements

Question 20

Rendering

Answer 20

creates the displayed image from the volume of echo data (allows certain image planes to be accentuated or shadowed)

Question 21

lobes

Answer 21

Extra off-axis sound beams can happen

Question 22

Side Lobes

Answer 22

These off-axis sound beams found at depth equal to and past the focus of single disk element probes

Question 23

Grating Lobes

Answer 23

Extra beams found along the length of the array transducers

Question 24

Subdicing

Answer 24

reduces grating lobes
A crystal is divided or “scored” into smaller crystals

Question 25

apodization

Answer 25

stronger electrical signals are used to excite the inner crystals, and progressively weaker electrical spikes excite the outer crystals

Question 26

dynamic aperture probe

Answer 26

progressively recruits more outer elements as it images deeper accomplishing a narrow beam over a substantial range of depth