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Flashcards in Chapter 2 Sound Edelman Deck (49):
0

What is a media?

biological tissue

1

What do waves carry from one location to another?

Energy

2

What kind of wave is sound?

a mechanical wave in which particles in the medium move

Must have a medium, cannot travel through a vacuum!!

3

What do acoustic propagation properties do?

the effects of the medium upon the sound wave

4

What are biological effects?

the effects of the sound wave upon the biologic tissue through which it passes

5

What is compression?

When molecules are squeezed together

6

What happens to molecules that are rarefied or rarefaction?

the molecules are stretched apart

7

What kind of line does sound travel in?

a straight line

8

What kind of waves are sound waves?

longitudinal waves

9

what ACOUSTIC VARIABLES are used to distinguish between sound waves and other types of waves?

pressure

density

distance

These create a traveling variation

10

What is pressure?

concentration of force in an area

Units: pascals (Pa)

11

what is another name for a sound wave?

acoustic wave

12

What has to happen to the acoustic variables of pressure, density, and distance in order for a SOUND wave to be created?

one of the acoustic variables has to have a rhythmic oscillation

13

what is a reflection?

it is the return of the sound wave from the structure to the transducer that produces an image

14

How do electromagnetic waves work?

They WILL work in medium or vacuum

15

What other kinds of waves are there?


These are electromagnetic waves:

light
heat
x rays
gamma rays
television signals
microwaves

16

what has to interact for sound to create a reflection?

Sound and a medium must interact

17

What does ultrasound interact with in the body?

US travels into the BODY SOFT TISSUE and interacts with the anatomy and allows us to produce diagnostic images

18

What is a Longitudinal sound wave?

travel in a straight line

particle motion is along the direction of the wave propagation

sound travels through COMPRESSIONS (squeezed together - regions of higher density and pressure) and RAREFACTIONS (stretched apart - regions of lower density and pressure)

19

What are acoustic propagation properties?

effects of the medium on the sound

20

What are biological effects?

effects of the sound on the biologic tissue

21

What is the definition of an acoustic variable?

identify sound waves and measure MECHANICAL CHANGES

22

What is density?

concentration of MASS in a VOLUME (kg/cm3)

23

What is distance?

measure of PARTICLE MOTION (mm, cm) a measurement of how far the particles travel

24

What are the acoustic PARAMETERS?

peroid

frequency

amplitude

power

intensity

wavelength

Propagation speed

25

What are "in phase" waves?

peaks and valleys at the same time

26

What are "out of phase" waves

peaks and valleys at different times (see slide for picture)

27

What are constructive waves?

pair of in phase waves resulting wave larger than components

28

What are destructive waves?

pair of out of phase waves - resulting wave smaller than components.

29

What is interference?

finish

30

What is the pulse echo principle?

finish

31

what is frequency?

number of cycles that occur in one second (cps - cycles per second...aka frequency)

one cycle per second is a Hertz (Hz)

On thousand Hertz - kilohertz

Finish

32

What are the frequency ranges?

Infrasound: less than 20 Hz

Audible sound: 20Hz - 20,000HZ or 20 kHz

Ultrasound: greater than 20,000 Hz or 20kHz

Medical diagnostic ultrasound :1 -15 MHZ

33

What are typical transducer frequencies in diagnostic imaging?

Lower frequencies = more penetration, but lack detail

Higher frequencies = less penetration but produce greater detail

select the highest frequency to get the best picture

34

how are parameters of sound waves determined?

by the source:
transducer
system

by the medium:
tissue

by the combination of medium and source

35

What is peroid?

A parameter of sound

TIME it takes a wave to vibrate a single cycle

units: TIME - microseconds

ultrasound imaging - 0.1 to 0.5 microseconds (very short amt of time) (microseconds made with the weird u thing)

determined by: the SOUND SOURCE only (the machine)

cannot be changed by the sonographer

period and frequency are INVERSELY related P=1/Frequency

36

What is frequency?

A parameter of sound

number of cycles that occurs in one second

Units: HERTZ (Hz) events per second

ultrasound imaging 1-15 MHz

determined by: the SOUND SOURCE only (the machine)

cannot be changed by the sonographer

infrasound - less than 20Hz

Audible sound - between 20Hz and 20kHz

37

How are frequency and period related?

inversely related

reciprocal

period x frequency = 1

38

What does frequency effect?

Penetration and AXIAL resolution

39

What is wavelength?

DISTANCE or length of one complete cycle

Units: DISTANCE - millimeters

US imaging: 0.15 -0.8 mm (tiny)

Determined by: BOTH the machine and the tissue

cannot be changed by the sonographer

wavelength= propagation speed/frequency

40

what is propagation speed?

a parameter of sound

DISTANCE that a sound wave travels through a medium in 1 second

units: distance/time = millimeters/microsecond

US imaging: soft tissue = ****1.54 mm/microsecond****

determined by: MEDIUM only

cannot be changed by the sonographer

speed changes when sound travels to different medium

**Speed = frequency x wavelength** (wavelength formula)

41

How do we find the wavelength in soft tissue?

in soft tissue to find the wavelength, divide 1.54 mm by the frequency in MHz

wavelength = 1.54 mm per microsecond/frequency

42

in what medium does sound travel fastest?

sound travels fastest in soilds

slower in liquids

slowest in gas

43

What are the relationships between different mediums and the speed of sound?

lung - 500 m/s

soft tissue (average) - 1540 m/s

bone - 3500 m/s

(slowest) air << fat<< soft tissue<< bone (fastest)

gas<< liquids << solids

44

What are the characteristics of the medium? Stiffness...

ability of an object to resist compression

retains its shape

stiffness and speed are directly related

bulk modulus aka: stiffness

inverse of compressibility

45

What are the characteristics of the medium? Density...

relative weight of a material

density and speed are inversely related

46

what is amplitude?

a bigness parameter

STRENGTH of the sound wave

difference between max or min and average value

units:
pressure -pascals

density - g/cm 3

particle motion - cm

relative - decibels -db

determined by: sound source (machine) INITIALLY, decreases through the body (atenuation)

can be controlled by the sonographer initially (adjusting the gain and increasing the amplitude)

47

What is power?

a bigness parameter

***the rate at which work is performed***

Units: watts

power is proportional to amplitude squared

determined by: INITIALLY by the sound source (machine)

can by controlled by the sonographer

decreases as propagating through the body

48

What is intensity?

bigness parameter

relates to the strength of the beam

concentration of energy

units: watts/cm2

determined by: Sound source INITIALLY
finish