Ch. 10 physics: Axial and Lateral Resolution

Question 1

A systems ability to distinguish between two structures that are lying close together.

Answer 1

Resolution

Question 2

The ability of a system to accurately display two very close structures that are parallel to the axis of the sound beam.

Answer 2

Axial Resolution

Question 3

Represents the minimum distance that two structures, positioned front-to-back, can be apart and still produce two distinct echoes on an ultrasound image.

Answer 3

Axial Resolution

Question 4

LARRD

Answer 4

Longitudinal

Axial

Range

Radial

Depth

Question 5

Shorter pulses have __________ axial resolution

Answer 5

Improved

Question 6

How are shorter pulses are created?

Answer 6

Less ringing

Higher frequency

Question 7

Is the axial resolution adjustable or non adjustable?

Answer 7

Not adjustable
Pulse length is fixed

Question 8

What is the clinical range of axial resolution?

Answer 8

0.1 - 1.0mm

Question 9

The ability to separate structures parallel to the ultrasound beam.

Answer 9

Axial Resolution

Question 10

Formula for axial resolution and spatial pulse length.

Answer 10

axial resolution (mm) = spatial pulse length (mm) / 2

Question 11

formula for axial resolution and wavelength.

Answer 11

Axial resolution (mm) = wavelength (mm) x # cycles in pulse / 2

Question 12

Formula for axial resolution in soft tissue.

Answer 12

Axial resolution (mm) = 0.77 x # cycles in pulse / frequency (MHz)

Question 13

True or false:
A pulse is longer if there are fewer cycles in the pulse

Answer 13

false
the pulse is shorter

Question 14

If a pulse is shorter with fewer cycles, this is known as…

Answer 14

Less ringing

Question 15

With fewer cycles in the pulse length, axial resolution …..

Answer 15

improves

Question 16

A pulse is short if each cycle in the pulse has a …..

Answer 16

Short wavelength

Question 17

High frequency and having shorter wavelengths =

Answer 17

Better axial resolution

Question 18

Better Axial Resolution is Associated with:

Answer 18

Shorter spatial pulse length

Shorter pulse duration

Higher Frequencies (shorter wavelengths)

Fewer cycles per pulse (less ringing)

Lower numerical values

Question 19

With axial resolution, Wavelength = ½ the PZT thickness, which means ….

Answer 19

thinner crystals equal shorter wavelengths resulting in higher frequency

Question 20

Thinner crystals means

Answer 20

Fast

Question 21

Thicker crystals means

Answer 21

Slow

Question 22

True or False:
Higher frequency is associated with shorter pulse length.

Answer 22

True

Question 23

True or False:
Fewer pulses per cycle will improve axial resolution.

Answer 23

True

Question 24

Which of the following choices would have the best axial resolution?

12 MHz, 2 cycles per pulse

6 MHz, 2 cycles per pulse

12 MHz, 4 cycles per pulse

6 MHz, 4 cycles per pulse

Answer 24

6 MHz, 2 cycles per pulse

Question 25

The ability to distinctly identify two structures that are very close together when they are perpendicular to the sound beams main axis.

Answer 25

Lateral Resolution

Question 26

Lateral resolution is also known as LATA, which means....

Answer 26

Lateral Angular Transverse Azimuthal resolution

Question 27

Lateral resolution is measured in .....

Answer 27

Distance (mm, cm)

Question 28

Lateral resolution is determined by

Answer 28

Beam width

Question 29

Lateral resolution changes with ______ due to _____

Answer 29

Depth divergence of the sound beam

Question 30

When two side-by-side reflectors are closer together than the beam’s diameter, only ______ reflection is seen on the image

Answer 30

one

Question 31

For lateral resolution, image is accuracy is best at _________

Answer 31

the focus

Question 32

the beam in lateral resolution is the narrowest at ________

Answer 32

The focus

Question 33

The structures located closer together than the beams diameter at the depth they are located, appear as one structure instead of ________

Answer 33

two

Question 34

Higher frequencies improve both _______ and _____________

Answer 34

axial Lateral resolution

Question 35

Axial is improved in the entire image with

Answer 35

shorter pulses

Question 36

Lateral is improved in the far field with

Answer 36

Less divergence

Question 37

Results in a narrower beam, improving lateral resolution

Answer 37

focusing the beam

Question 38

What are the types of focusing?

Answer 38

Fixed, Conventional, or Mechanical

Question 39

How do you focus externally?

Answer 39

with a lens

Question 40

How do you focus internally?

Answer 40

with a curved active element

Question 41

How is Phased array focused?

Answer 41

with the electronics of the ultrasound system

Question 42

Phased array is adjustable or not adjustable?

Answer 42

adjustable

Question 43

A fixed focusing technique where a lens is placed in front of the PZT

Answer 43

External focusing

Question 44

As the arc of the lens becomes more prominent in external focusing, ......

Answer 44

the degree of focusing increases and the beam narrows

Question 45

The PZT is curved, concentrating its energy and creating a narrow beam, improving the beams focus and is the most common form of fixed focusing used. Is this internal focusing or external focusing?

Answer 45

Internal focusing

Question 46

What type of focus is achieved through phased array transducers?

Answer 46

Electrical focusing

Question 47

What does phased array mean?

Answer 47

Adjustable or multiple focusing

Question 48

What kind of transducers use phased array?

Answer 48

Multi-element transducers only

Question 49

True or false: Electronic focusing allows the sonographer the ability to alter the beams focus.

Answer 49

True

Question 50

How can the Sonographer alter the electronic focus?

Answer 50

By beam steering

Question 51

What are the 4 modifications a sound beam goes through to be electronically focused?

Answer 51

The beam diameter in the near field and the focal zone narrows Near zone length is reduced The beam diameter beyond the focal zone widens Size of the focal zone is reduced

Question 52

Where is the lateral resolution better in the beam?

Answer 52

Where it is narrow

Question 53

If the transducer crystal diameter is 10 cm, what is the lateral resolution at the focus?

Answer 53

5cm remember the lateral resolution = beam diameter The beam diameter is ½ the crystal diameter at the focus.

Question 54

Which of the following transducers have the poorest axial resolution? 2.5 MHz and 2 cycles/pulse 3 MHz and 4 cycles/pulse 2.5 MHz and 4 cycles/pulse 3 MHz and 2 cycles/pulse

Answer 54

2.5 MHz and 4 cycles/pulse

Question 55

In soft tissue, a 4 cycle, 2MHz pulse has a pulse length equal to 6 mm. What is the axial resolution?

Answer 55

3 mm the axial resolution = ½ the spatial pulse length

Question 56

A transducer with more cycles per pulse will have greater/lower axial resolution?

Answer 56

Lower

Question 57

Which of the following terms does not belong with the others? Longitudinal Range Azimuthal Radial

Answer 57

Range

Question 58

What is the most common form of fixed focusing?

Answer 58

internal

Question 59

What is electronic beam focusing called?

Answer 59

Phased

Question 60

Single crystal transducers are always (fixed/phased) focusing?

Answer 60

Fixed