Imaging Resolution

Question 1

Sector transducers are good at creating better resolution. What type of resolution is this?

Answer 1

Temporal resolution

Question 2

How to improve axial resolution?

Answer 2

1. Increased frequency - decreases wavelength
2. Dampening material on transducer (less ringing and listening which decreases SPL)
3. Shorter SPL

Question 3

What is the formula for axial resolution?

Answer 3

SPL/2

Question 4

If SPL is 12mm, will structures that are 7mm apart be distinguished separately?

Answer 4

AR must be equal or greater than the SPL/2.

12mm/2 = 6mm, so structures MUST be at least 6mm or greater apart to be seen as separate

Question 5

If SPL is 12mm, will structures 4mm apart be distinguished separately?

Answer 5

NO, since the formula is 12mm/2 = 6mm, structures less than 6mm apart will not be distinguished separately

Question 6

Lateral resolution is equal to what?

Answer 6

The beam width

Question 7

How to improve lateral resolution?

Answer 7

Focusing - the best LR is at or just before the focus

Question 8

What does multiple foci do to lateral resolution and temporal resolution?

Answer 8

Improves lateral resolution

Decreases temporal resolution

Question 9

Where is the best lateral resolution?

Answer 9

At or just BEFORE the focus

Question 10

How do you change the focus to improve lateral resolution?

Answer 10

1. Changing the aperture (number of crystals)
2. Phasing

Question 11

Where should you place the focus to improve lateral resolution?

Answer 11

At or just BELOW the area of interest

Question 12

Where is the highest intensity of the beam?

Answer 12

At or just before the focus

Question 13

What is the elevational plane also known as?

Answer 13

The slice thickness plane

Question 14

What artifact is seen in the elevational plane?

Answer 14

Slice thickness/partial volume artifact

Question 15

What is elevational resolution dependent on?

Answer 15

1. Lens
2. Size and shape of the crystal

Question 16

How to improve elevational resolution?

Answer 16

Harmonics

Question 17

What types of resolution is improved with harmonics?

Answer 17

Lateral and elevational

Question 18

What type of artifact creates a “filling in” of anechoic structures to become more echoic?

Answer 18

Slice thickness artifact/partial volume

Question 19

Does slice thickness artifact occur when the slice thickness is larger or smaller than the size of the structure?

Answer 19

Larger

Question 20

What type of resolution has the ability to display and differentiate structures based on varying levels of brightness?

Answer 20

Contrast resolution

Question 21

How many shades of grey are on ultrasound imaging?

Question 22

How can contrast resolution be changed by the sonographer?

Answer 22

1. Gains
2. TGC’s
3. Compression
4. Dynamic Range

Question 23

How do you change the number of shades of grey on ultrasound?

Answer 23

Dynamic range buttom

Question 24

What gives the best contrast resolution based on dynamic range and compression?

Answer 24

Decreased dynamic range and increased compression

Question 25

Will increasing the dynamic range improve or degrade contrast resolution?

Answer 25

Degrades

Question 26

What resolution is based on the image constantly changing due to the motion of structures?

Answer 26

Temporal resolution

Question 27

What is temporal resolution dependent on?

Answer 27

1. Frame rate/ lines per frame
2. Depth of the beam
3. Sector width
4. Multiple focuses

Question 28

What is temporal resolution highly dependent on?

Answer 28

Frame rate

Question 29

How to IMPROVE temporal resolution?

Answer 29

1. Decreased depth
2. Decreased sector width
3. Decreased scan lines

Question 30

What happens to the frame rate when you increased the frequency?

Answer 30

Increase FR

Question 31

When is multiple foci helpful?

Answer 31

In static imaging, especially for breast and liver