Lesson 4 (Part 1) Flashcards Preview

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Flashcards in Lesson 4 (Part 1) Deck (26)
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1

If frequency increases, what happens to the wavelength? How does this effect the image?

1. Wavelength decreases
2. Leads to a better quality in photos

2

If frequency decreases, what happens to the wavelength? How does this effect the image?

1. Wavelength increases
2. Leads to a poorer quality in photos

3

What do different transducers have?

Different frequencies

4

What is the frequency that you choose called?

Fundamental frequency

5

What are 2 other names for fundamental frequency?

1. Operating frequency
2. Transmit frequency

6

Why do we have listening time?

The ultrasound needs to receive all of the echoes back

7

What happens to pulse duration if frequency increases?

It decreases

8

What happens to spatial pulse length if frequency decreases?

It increases

9

When do you use higher frequencies?

When you are scanning superficially
- less penetration

10

What do high frequencies produce?

Better quality image

11

When do you use lower frequencies?

When you are scanning deeper in the body
- better penetration

12

What do low frequencies produce?

Worse quality images

13

What is one way to achieve high frequency waves in order to get better quality images?

The use of harmonics

14

What is a basic sound wave an example of?

Sinusoidal waveform

15

Sinusoidal waveform

Continuous smooth periodic oscillations

16

Does sound change shape when it travels through tissues?

Yes
- sinusoidal to non-sinusoidal

17

Non linear propagation

Changing the wave shape

18

Do more dense areas move faster or slower?

Faster

19

Do less dense areas move faster or slower?

Slower

20

What do nonsinusoidal waves contain?

Additional frequencies
- even and odd multiples of fundamental frequencies

21

What does it mean when you have less sinusoidal shape?

Stronger harmonics

22

Harmonics

Send out one frequency, get back several higher frequencies

23

Pulse

A few cycles of ultrasound

24

What are pulses separated by in pulse waves?

Separated in time by gaps of no ultrasound

25

Pulsed wave

A pulse that is followed by a gap
- listening time and downtime

26

Why do we have a gap in pulsed waves?

So we can listen