Module 4: Resolution

Question 1

Resolution can be broken down into what three aspects?

Answer 1

1. Detail
2. Contrast
3. Temporal

Question 2

Detailed resolution can be further divided in what three aspects?

Answer 2

1. Axial
2. Lateral
3. Elevational

Question 3

What is axial resolution?

Answer 3

The ability to separate reflects along the path of the beam

Question 4

Axial resolution is dependent of what? and is calculated how?

Answer 4

Dependent of SPL and is calculated by 1/2 the SPL

Question 5

What is the formula for spatial resolution?

Answer 5

AR = (1/2) SPL

Question 6

If SPL decreases what happens to axial resolution?

Answer 6

It improves

Question 7

Axial resolution is known by what of the following names?

Answer 7

1. Longitudinal
2. Range
3. Depth

Remember LARD

Question 8

What is lateral resolution?

Answer 8

The ability to separate reflectors perpendicular to the path of the beam

Question 9

Lateral resolution is dependent of what?

Answer 9

The width of the beam and therefore, is not constant with depth

Question 10

What does this image represent?

Answer 10

Lateral resolution

Question 11

Lateral resolution is directly related to what?

Answer 11

The width of the beam

Question 12

If the beam width decreases then what?

Answer 12

Lateral resolution improves

Question 13

Lateral resolution is known by what other names?

Answer 13

1. Angular
2. Transverse
3. Azimuthal

Remember LATA

Question 14

What is elevational resolution?

Answer 14

Also known as slice thickness this is the ability to separate reflectors perpendicular to the image plane of the beam

Question 15

Elevational resolution is dependent on what aspect of the beam?

Answer 15

Width of the beam but in Z axis

Question 16

Elevational resolution is directly related to what?

Answer 16

The width of the beam in the Z axis

Question 17

If beam width in the Z axis decreases then what happens?

Answer 17

Elevational resolution improves

Question 18

Elevational Resolution is also known as what?

Answer 18

Slice thickness

Question 19

What is contrast resolution?

Answer 19

The ability to distinguish subtle differences in tissue gray scale

Question 20

What is contrast resolution related to?

Answer 20

Bit depth

Question 21

For contrast resolution, having a higher bit depth means what?

Answer 21

The more shades of tray the system is capable of displaying

Question 22

More shades of gray gives the operator what?

Answer 22

More control over the dynamic range

Question 23

By reducing the dynamic range the sonographer may increase the ability to do what?

Answer 23

Distinguish once subtle differences in grayscale

Question 24

What is temporal resolution?

Answer 24

The ability to appreciate moving structures in real time

Question 25

What is temporal resolution related to?

Answer 25

System frame rate

Question 26

Temporal resolution is directly related to what?

Answer 26

Frame rate

Question 27

If frame rate increases then what happens?

Answer 27

Temporal resolution improves

Question 28

Since temporal resolution is defined by frame rate, what else is frame rate related to?

Answer 28

PRF

Question 29

What is the formula for temporal resolution?

Answer 29

PRF(Hz) = n x LPF x FR(Hz) n = number of foci LPF = lines per frame FR = frame rate or frames per second

Question 30

Penetration of sound plays an important role in what?

Answer 30

PRF

Question 31

What is the formula for sound penetration?

Answer 31

Penetration (cm) x n x LPF x FR < 77,000 cm/s

Question 32

Why do we use 77,000 for penetration of sound?

Answer 32

Because it represents half the average speed of sound in soft tissue (154,000 cm/s)

Question 33

What things relate to better axial resolution? 5

Answer 33

1. Higher frequency probes 2. Wide bandwidth 3. Decreased wavelength 4. Increased damping 5. Low Q factor

Question 34

What things relate to better lateral resolution?

Answer 34

1. Distance from the probe 2. Amount of focusing 3. Size of aperture 4. NZL 5. Higher the frequency

Question 35

What things relate to better elevational resolution?

Answer 35

1. Distance from the probe 2. Higher the frequency 3. NZL 4. Amount of focusing in the Z plane

Question 36

What things relate to better temporal resolution? 5

Answer 36

1. Depth of penetration 2. The number of foci 3. The sector width 4. Frame rate 5. The number of lines per frame