Chapter 13 ultrasound physics

Static scanning

When images are displayed one frame at a time.

Frame Rate

The systems ability to create numerous frames each second.

Frame rate is determined by?

-Sound's speed in the medium.

-the depth of imaging

Frame rate unit?

Hz

Temporal resolution?

Pertains to "accuracy in time," describes the ability to precisely position moving structures from instant to instant.

Temporal resolution is determined by?

Frame rate

Temporal resolutions units?

Hz

T-frame?

Time it takes to make one frame.

20 frames per second. How much time will it take to make 1 frame?

1/20th of a second.

Frame rate and T-frame are ______ related?

Inversely. (Reciprocals)

What determines the ultrasound systems frame rate?

-imaging depth

-# of pulses per frame.

Shallow imaging _____ frame rate and ______ temporal resolution.

Increases; improves

Deeper imaging ____ frame rate and _____ temporal resolution.

Decreases;degrades

I'm aging depth and frame rate are ______ related.

Inversely

T frame's equation?

# pulses x PRP

Frame rate unit?

Hz

T frames unit?

Seconds

If a sound pulse has a PRP of 0.01 seconds. What will be the frame time if 10 sound pulses are used to construct a frame?

0.01 x 10

1/10

(Take reciprocal)

10 Hz.

Pulses per frame and frame rate are _____ related.

Inversely

3 Factors determining number of pulses per frame?

-number of focal points

-sector size

-line density

Single focus has?

Better temporal resolution and poor lateral resolution.

Multi-focus has?

Diminished temporal resolution and improved layers resolution.

Line density?

Altering the space between sound beams.

When line density is low, few pulses create each image and the frame rate is______?

High

When line density is high, the number of pulses per image ____ , frame rate _____ and temporal resolution ______.

Increases; drops; decreases

If temporal resolution increases then image detail ______.

Decreases.

Image detail is also known as?

Spatial resolution.

Temporal resolution is the same thing as ?

Frame rate.

With stationary structures, frame rate ___, image quality ____ and temporal resolution _____.

Decreases;increases;decreases.

Moving structures have ____ frame rate, ____ image quality and ____ temporal resolution.

Increases;decreases;increases

Better temporal resolution has ____ frame rate.

Higher

Lateral resolution improves with?

Multi focusing

Spatial resolution improves with ?

High line density

A sonographer adjusts an ultrasound scan to double the depth of view from 5 cm to 10 cm. if the frame rate remains the same, what happens to the sector?

Narrows.

A sonographer reduces the sector angle from 90 degrees to 30 degrees. At the same time, the ultrasound system automatically increases the line density from 1 line per degree to 2 lines per degree. No other changes are made. What will happen to the frame rate?

Increases.

What is the most important in determining the frame rate of a system?

Speed of sound in the medium.

What is the time needed to make a single image if the frame rate of an ultrasound system is 20 Hz?

0.05 seconds.

If you increase the PRF and leave all other controls unchanged, what will happen?

Frame rate will increase