US physics quiz 2

Axial Resolution

controlled by spatial pulse length (SPL)

Lateral Resolution

controlled by beam width

Elevational Resolution

controlled by slice thickness

Temporal Resolution

controlled by frame rate

Spatial Resolution

• Ability to accurately display structural detail

Includes:

• Axial Resolution

• Lateral Resolution

• Elevational Resolution

Temporal Resolution

• Ability to accurately display motion over time

Determined primarily by:

• Frame Rate

• Imaging Depth

• Number of Scan Lines

• Number of Focal Zones

better axial resolution

shorter SPL (spatial pulse length)

resolved or unresolved

resolved

resolved or unresolved

unresolved

which scenario has better axial resolution?

A) SPL= 4mm

B) SPL= 2mm

SPL = 2mm

Shorter SPL Occurs With:

• Fewer cycles per pulse

• Higher frequency → Shorter wavelength

• Increased damping (backing material)

Which change would MOST improve axial resolution?

a) Increase imaging depth

b) Increase transducer frequency

c) Increase beam width

d) Increase dynamic range

b) Increase transducer frequency

better lateral resolution

narrow beam width

Good Lateral Resolution

• Narrow beam width

• Side by side reflectors displayed separately

• Improved detail across the image

Poor Lateral Resolution

• Wide beam width

• Side by side reflectors blur together

• Reflectors may appear as one structure

Best Lateral Resolution Occurs:

• At the focal zone

• Where the beam is narrowest

Which image demonstrates BETTER lateral resolution and

WHY?

Image B

• Better side by side reflector separation

• Improved lateral resolution

• Narrower beam width

Which adjustment would MOST improve lateral resolution?

a) Increase imaging depth

b) Increase beam width

c) Place the focal zone at the area of interest

d) Increase dynamic range

c) Place the focal zone at the area of interest

better elevational resolution

narrow slice thickness

Which artifact is demonstrated in this image and why?

a) Reverberation

b) Slice thickness artifact

c) Mirror image artifact

d) Shadowing

b) Slice thickness artifact

Good Elevational Resolution

• Thin slice thickness

• Structures within the imaging plane displayed accurately

• Reduced partial volume artifact

Poor Elevational Resolution

• Thick slice thickness

• Echoes from outside the imaging plane included in the image

• May create false internal echoes

A sonographer notices low level echoes appearing within a simple cyst that should be anechoic.

Which type of resolution is MOST likely contributing to this artifact?

a) Axial resolution

b) Temporal resolution

c) Elevational resolution

d) Contrast resolution

c) Elevational resolution

better temporal resolution

higher frame rate

Frame Rate Increases With:

• ↓ Depth

• ↓ Scan Lines

• Narrower Sector Width

• Fewer Focal Zones

Frame Rate Decreases With:

• ↑ Depth

• ↑ Scan Lines

• Wider Sector Width

• Multiple Focal Zones

relationship between frame rate and temporal resolution

↓ Frame Rate → ↓ Temporal Resolution

A sonographer increases imaging depth during an abdominal scan.

What happens to:

• Frame rate

• Temporal resolution

Frame rate and temporal resolution decreases

Output Power affects

the transmitted beam

Overall Gain affects

the displayed image brightness

If the entire ultrasound image appears too dark, what adjustment should be made FIRST?

a) Increase output power

b) Increase overall gain

c) Increase imaging depth

d) Increase dynamic range

b) Increase overall gain

TGC adjusts brightness by

depth, not the entire image uniformly

What adjustment is MOST appropriate?

a) Increase overall gain

b) Increase far field TGC

c) Increase output power

d) Increase dynamic range

b) Increase far field TGC

A sonographer notices that the far field of the image appears too dark, while the near field brightness appears appropriate.

Which adjustment is MOST appropriate?

a) Increase overall gain

b) Increase output power

c) Adjust far field TGC

d) Increase frame rate

c) Adjust far field TGC

Wide Dynamic Range

More Gray Shades

Narrow Dynamic Range

Higher Contrast

Which adjustment would produce a higher contrast image with fewer shades of gray?

a) Increase dynamic range

b) Decrease dynamic range

c) Increase frame rate

d) Increase beam width

b) Decrease dynamic range

Image appears globally too dark

Best Adjustment:

increase overall gain

Only the far field appears too dark

Best Adjustment:

adjust far field TGC

Motion appears blurred during cardiac imaging

Best Adjustment:

Increase frame rate:

• decrease depth

• decrease sector width

• reducing focal zones

Side by side structures appear poorly separated

Best Adjustment:

improve lateral resolution:

• focal zone placement

A sonographer is performing cardiac imaging and notices:

• Motion appears blurred

• Frame rate is low

• Multiple focal zones are activated

• Imaging depth is excessive

Which combination of adjustments would MOST improve

temporal resolution?

a) Increase imaging depth and increase dynamic range

b) Reduce imaging depth and reduce focal zones

c) Increase beam width and increase gain

d) Increase TGC and increase sector width

b) Reduce imaging depth and reduce focal zones

As transducer frequency increases, spatial pulse length will:

a) Increase

b) Decrease

c) Remain unchanged

d) Double

b) Decrease

If the time required to produce a single image frame increases, temporal resolution will:

a) Improve

b) Remain unchanged

c) Decrease

d) Double

c) Decrease

A sonographer adds multiple focal zones during imaging.

What is the MOST likely effect?

a) Improved temporal resolution

b) Increased frame rate

c) Improved lateral resolution with decreased frame rate

d) Improved axial resolution

c) Improved lateral resolution with decreased frame rate

A sonographer changes from a 3 MHz transducer to a 10 MHz transducer.

What is the MOST likely result?

a) Improved penetration and decreased resolution

b) Decreased attenuation and decreased resolution

c) Improved axial resolution and decreased penetration

d) Increased beam width and decreased frame rate

c) Improved axial resolution and decreased penetration