Transducer Evolution

Question 1

What transducers used single crystals

Answer 1

Old static B scanners

Early real time units

Question 2

What transducers use electronic array

Answer 2

Mechanical probes in modern day units

Question 3

Mechanically steered probes to obtain field of view

Answer 3

Single disc element housed

Prone to break down

Question 4

Probe evolution

Answer 4

Single disc
Mechanically steered
Angular array
Electronic array

Question 5

Mechanical transducer

Answer 5

Started out as thin disk-shaped crystal about 6 to 19mm in diameter
Fixed vocal zone

Question 6

Linear translation

Answer 6

Oldest technology moved the crystal along a track to sweep the tissue

Question 7

Wobbler probe

Answer 7

Fixed an element onto a motor that rotated back and forth to obtain a field of view
Very popular probe
Produced a sector type image
Fluid filled, moving parts risked the production of air bubbles

Question 8

Linear field of view

Answer 8

To archives this probes would use a felectod or acoustic mirror or direct the sound into the patient

Question 9

Oscillating mirror

Answer 9

The mirror moves with the stationary element

Question 10

Rotating wheel probes

Answer 10

Have several crystals that spin

Only pulse when the element passes the field of view

Question 11

Angular array

Answer 11

One of the biggest advances in transducer technology

Still mechanically steered, had the ability to dynamically change the focus was now possible

Question 12

Angular array uses

Answer 12

Concentric discs to allow for focusing of the beam

Changing the disc , changes the diameter which varies the focal depth

Question 13

Wider the crystal

Answer 13

Deeper the transition point

Question 14

Transition zone equals

Answer 14

Convergence beam to divergence beam

Question 15

Problem of the angular array

Answer 15

Same limitation of mechanically steered probes

Produces grating lobes

Question 16

Grating lobes

Answer 16

Low energy beams that radiate away from the main axis and contribute to artifacts

Question 17

Side lobes

Answer 17

Grating lobes

Question 18

Electronic arrays

Answer 18

Have multiple small elements aligned in linear rows
Have wide bandwidths and have the flexibility to perform other applications such as colour/spectral Doppler, m-mode, power Doppler

Question 19

Two main types of arrays

Answer 19

Phased sector array

Phased linear array

Question 20

Phasing

Answer 20

Uses nanosecond time delays to change when the voltage excites the crystal
Purpose is to control the beam and allow for beam focusing and steering

Question 21

Steering of the beam

Answer 21

Can help direct the sound out of an angle as is the case for the phased sector array, Doppler and vector scanning

Question 22

Vector scanning

Answer 22

Another term for describing steering the beam

Question 23

What is a good way to determine the direction of the beam

Answer 23

To slope of the delayed voltages

Question 24

Phased array

Answer 24

All crystals are fired at early the same time to steer the beam across the fac of the probe
For can be as large as 90° or as small as 30°

Question 25

Linear array

Answer 25

Tend to have relatively large footprints with approx 64-200 elements arranged in a row
FOV is a rectangular shape but can be trapezoidal if scanning in vector mode
Means no scan line divergence
Are used in many applications of ultrasound, tend to be associated with higher frequencies

Question 26

How is the beam swept across the transducer face with the linear array

Answer 26

Firing a small single element will increase divergence which equates to a broad beam resulting in poor resolution and sensitivity
Takes away the abolition to electronically focus or steer the sound

Question 27

Larger point source of sound would have

Answer 27

Less divergence and the resolution improve as would the sensitivity

Question 28

Firing in segments

Answer 28

Enables electronic transmit focusing and steering

At the cost of fewer scan lines which can degrade the images spatial resolution

Question 29

Segmental sequencing

Answer 29

A group of crystals is fired to create a beam followed by a second group that is one crystal down in the row

Question 30

Curved linear

Answer 30

Uses the same principle of the linear array
Uses small rectangular shaped elements that are curved
Beam angles appear like the spokes of a wheel

Question 31

Advantage of the curved linear probe

Answer 31

Large footprint and FOV

Possible to see well in the near and far field

Question 32

Disadvantage of the curved linear probe

Answer 32

Is the resolution in the far field can be degraded as the distance between beams is increased

Question 33

Apodization

Answer 33

The voltages to the crystals are gradually weakened from the inside out
This is used to correct for the process of grating lobes

Question 34

Obtaining 3D and 4D images can be done in 2 ways

Answer 34

Freehand using a traditional array probe

Volumetric probe

Question 35

Volumetric probe

Answer 35

Beam is swept over the area of interest to obtain the information for 3D reconstruction

Question 36

Intravascular probes

Answer 36

Capable of scanning from within the lumen of the vessel

Question 37

Transesophageal echo probes

Answer 37

TEE

Can improve the visualization of the heart

Question 38

Specialty probes

Answer 38

Multiple types

Exist for biopsies, intervention and endocavitary exams

Question 39

Dedicated CW probes

Answer 39

Contain 2 crystals where one transmits and the other receives
Are air backed and have continuous AC driving voltage
Vascular: pencil probe
Echo: ped-off probe

Question 40

Zone of sensitivity

Answer 40

Sample volume for continuous wave probes