Physics Principles

Question 1

process whereby sound energy is dissipated in a medium, primarily in the form of heat

Answer 1

absorption

Question 2

having to do with sound

Answer 2

acoustic

Question 3

resistance of sound as is propagates through a medium

Answer 3

acoustic impedance

Question 4

effects on sound beam caused by the medium; includes pressure, density, and particle motion (distance and temperature)

Answer 4

acoustic variables

Question 5

realting to the strength of the compression wave; max variation of an acoustic variable

Answer 5

amplitude

Question 6

attenuation occurring with each centimeter that sound travels

Answer 6

attenuation coefficient

Question 7

range of frequencies found in pulse ultrasound

Answer 7

bandwidth

Question 8

distance around the perimeter of an object

Answer 8

circumference

Question 9

region of high pressure or density in a compression wave

Answer 9

compression

Question 10

a nonplused wave in which cycles repeat indefinitely

Answer 10

continuous wave

Question 11

one complete variation in pressure or other acoustic variable

Answer 11

cycle

Question 12

a unit used to compare the ratio of intensities or amplitudes of two sound waves or two points along the wave

Answer 12

decibel

Question 13

concentration of mass, weight, or matter per unit volume

Answer 13

density

Question 14

dependence of velocity of other physical parameters on frequency

Answer 14

dispersion

Question 15

amount of space from one object to another

Answer 15

distance

Question 16

fraction of time that pulse ultrasound is on

Answer 16

duty factor

Question 17

capability of doing work

Answer 17

energy

Question 18

comparison of range of frequencies (bandwidth) with operating frequency

Answer 18

fractional bandwidth

Question 19

number of cycles in a wave occurring in 1 second

Answer 19

frequency

Question 20

original operating frequency

Answer 20

fundamental frequency

Question 21

thickness of tissue required to reduce the intensity of the sound beam by one-half; also known as depth of penetration, half boundary layer, or penetration depth

Answer 21

half value layer (HVL)

Question 22

echoes of twice the frequency transmitted into the body that reflect back to the transducer, which improves image quality

Answer 22

harmonic frequency

Question 23

once cycle per second; unit of frequency

Answer 23

hertz (Hz)

Question 24

determines how much of an incident sound wave is reflected back from the first medium and how much is transmitted into the sound beam

Answer 24

impedance

Question 25

direction of incident beam with respect to the media boundary

Answer 25

incident angle

Question 26

initial or staring beam

Answer 26

incident beam

Question 27

rate at which energy transmits over a specific area

Answer 27

intensity

Question 28

one thousand cycles per second

Answer 28

kilohertz (kHz)

Question 29

wave traveling in straight line

Answer 29

longitudinal wave

Question 30

incident ultrasound traveling at an oblique angle to the media boundary

Answer 30

oblique incidence

Question 31

time to complete one cycle

Answer 31

period

Question 32

incident ultrasound traveling at an angle perpendicular to the media boundary

Answer 32

perpendicular incidence

Question 33

concentration of force

Answer 33

pressure

Question 34

speed at which a wave moves through a medium

Answer 34

propagation speed

Question 35

a collection of a number of cycles that travel together

Answer 35

pulse

Question 36

portion of time from the beginning to the end of a pulse

Answer 36

pulse duration

Question 37

number of pulses per second

Answer 37

pulse repetition frequency

Question 38

time between the beginning of one cycle and the beginning of the next cycle

Answer 38

pulse repetition period

Question 39

a few pulses of ultrasound followed by a longer pause of no ultrasound.

Answer 39

pulse ultrasound

Question 40

for short pulses, the Q factor is equal to the number of cycles in a pulse; the lower the Q factor the better the image

Answer 40

Quality Factor (Q factor)

Question 41

regions of low pressure or density in a compression wave

Answer 41

rarefaction

Question 42

occurs when the reflector is much smaller than the wavelength of the sound beam

Answer 42

Rayleigh's Scatter

Question 43

the beam redirected back to the transducer after striking a media boundary

Answer 43

reflected beam

Question 44

redirection (return) of a portion of the sound beam back to the transducer

Answer 44

reflection

Question 45

angle between the reflected sound and a line perpendicular to the media boundary

Answer 45

reflection angle

Question 46

change in direction of the sound wave after passing from one medium to another

Answer 46

refraction

Question 47

redirection of sound in several directions on encountering a rough surface; also known as nonspecular reflections

Answer 47

scattering

Question 48

a traveling variation of acoustic variables

Answer 48

sound

Question 49

relating to space

Answer 49

spatial

Question 50

multiple echoes received at the same time generating interference in the sound wave, resulting in a grainy appearance of the sonogram

Answer 50

speckle

Question 51

distance over which a pulse occurs

Answer 51

spatial pulse length

Question 52

these comprise the boundaries of organs and reflect sound in only one direction; angular dependent

Answer 52

specular reflections

Question 53

these comprise the boundaries of organs and reflect sound in only one direction; angular dependent

Answer 53

specular reflections

Question 54

resistance of a material to compression

Answer 54

stiffness

Question 55

relating to time

Answer 55

temporal

Question 56

the sound beam continuing on to the next media boundary

Answer 56

transmitted beam

Question 57

amount of occupied space of an object in three dimensions

Answer 57

volume

Question 58

distance (length) of one complete cycle

Answer 58

wavelength

Question 59

below 20Hz; below human hearing

Answer 59

infrasound

Question 60

Above 20Hz and below 20,000Hz; within human hearing

Answer 60

audible sound

Question 61

Above 20,000Hz (20kHz); above human hearing

Answer 61

ultrasound

Question 62

Sound waves carry _____ not matter, from one place to another.

Answer 62

energy

Question 63

``` Give the values and symbol for the following metric prefixes: Tetra Giga Mega Kilo Hecto Deca deci centi milli micro nano pico ```

Answer 63

``` Tetra = trillion 10^12 = T Giga = billion 10^9 = G Mega = million 10^6 = M Kilo = thousand 10^3 = k Hecto = hundred 10^2 = h Deca = ten 10^1 = Da deci = tenth 10^-1 = d centi = hundredth 10^-2 = c milli = thousandth 10^-3 = m micro = millionth 10^-6 = u (the special looking u) nano = billionth 10^-9 = n pico = trillionth 10^-12 = p ```

Question 64

Whats the propagation speed in soft tissue?

Answer 64

1.54mm/us or 1540 m/s

Question 65

in soft tissue what is the attenuation coefficient equal too?

Answer 65

half the transducer frequency

Question 66

attenuation happens as a result of?

Answer 66

absorption reflection scattering

Question 67

``` what are the units of the following: attenuation attenuation coefficient density half value layer impedance ```

Answer 67

``` attenuation = dB attenuation coefficient = dB/cm density = kg/m^3 half value layer = cm impedance = rayls ```