Week 1 - US Basics

Question 1

audible sound range

Answer 1

20 - 20k Hz

Question 2

ultrasound range

Answer 2

> 20 kHz

Question 3

Diagnostic Ultrasound range

Answer 3

1MHz - 20 MHz

Question 4

what are waves

Answer 4

disturbance away from average condition which carries only energy

Question 5

types of waves

Answer 5

mechanical & electromagnetic

Question 6

mechanical waves ___

Answer 6

propagate through physical mediums like sound & water

Question 7

electromagnetic waves ___

Answer 7

travel through space/vacuum without needing a physical medium such as heat & x-rays

Question 8

types of mechanical waves

Answer 8

transverse + longitudinal

Question 9

transverse wave particles move ___

Answer 9

perpendicular to direction of wave propagation

Question 10

longitudinal wave particles move ___

Answer 10

parallel / anti-parallel to wave motion; oscillate back and forth in their resting positions

Question 11

variables of sound

Answer 11

wave speed, frequency, wavelength

Question 12

speed of sound is dependent on ___

Answer 12

media density & compressibility

Question 13

speed of sound is constant for particular medium as long as temperature is ___

Answer 13

constant

Question 14

the average speed of soft tissue using ultrasound is ___

Answer 14

1540m/s

Question 15

the denser the medium, the ___ the sound wave propagation

Answer 15

slower

Question 16

density refers to the __

Answer 16

number of particles per unit volume

Question 17

compressibility refers to

Answer 17

how easy the volume of material can change

Question 18

the more compressible the medium is, the __ sound waves propagate

Answer 18

faster

Question 19

compressibility & density of a substance are ___

Answer 19

interdependent

Question 20

1 kHz is ___ cycles per sec

Answer 20

1000

Question 21

diagnostic ultrasound frequency

Answer 21

2 - 18 MHz

Question 22

ultrasound wavelength ranges between ____

Answer 22

0.1 to 1.0mm

Question 23

Attenuation

Answer 23

redirected energy that is lower in energy compared to incident wave

Question 23

sound & matter interactions

Answer 23

SARR

Scattering, Attenuation, Reflection, Refraction

Question 24

For attenuation, the deeper the wave travels in the body, the ___ it becomes

Answer 24

weaker

Question 25

attenuation =

Answer 25

absorption + scattering

Question 26

what happens to the tissue during absorption

Answer 26

tissue energy content increases while beam intensity decreases during transmission

Question 27

intensity loss formula

Answer 27

intensity loss = μ x f x z μ = intensity attenuation coefficient z = distance travelled in cm

Question 28

attenuation coefficient is the ___

Answer 28

loss of intensity in decibels per tissue cm traversed per megahertz

Question 29

attenuation coefficient is ___ proportional to frequency

Answer 29

directly

Question 30

attenuation coefficient unit is __

Answer 30

dB/cm

Question 31

attenuation factors

Answer 31

tissue type, frequency, depth

Question 32

low frequency = ____ depth of penetration

Answer 32

high

Question 33

acoustic impedance is defined as the ____

Answer 33

medium resistance to sound transmission

Question 34

acoustic impedance formula

Answer 34

Z (acoustic impedance) = p (density) x c (sound velocity)

Question 35

acoustic impedance unit

Answer 35

rayl

Question 36

if acoustic impedance in 2 mediusm are the same, sound will travel ___

Answer 36

readily from one to another

Question 37

if acoustic impedance in 2 mediusm are not the same, a portion of the sound will be ___

Answer 37

reflected at interface

Question 38

what allows for visualization of soft tissue structures within US beam

Answer 38

acoustic impedance

Question 39

difference in acoustic impedance between 2 tissues causes ___

Answer 39

sound wave reflection

Question 40

reflection is determined by ___ of interface

Answer 40

size & surface

Question 41

reflections occur at ___ between 2 adjacent tissues

Answer 41

boundary / interface

Question 42

reflection coefficient

Answer 42

amount of US beam reflected at interface

Question 43

% reflection of fat/muscle

Answer 43

1.08

Question 44

% reflection of fat/kidney

Answer 44

0.6

Question 45

% reflection of soft tissue / water

Answer 45

0.2

Question 46

% reflection of bone/fat

Answer 46

49

Question 47

% reflection of soft tissue / air

Answer 47

99

Question 48

specular reflection

Answer 48

US strikes smooth boundary = interface large & relatively smooth with max reflection at 90 degrees

Question 49

non-specular reflection

Answer 49

US strikes boundary w/ irregular surface & multiple interfaces = sound deflects in multiple directions

Question 50

refraction follows what law

Answer 50

snell's law

Question 51

greater diff of velocity = __ refraction

Answer 51

increased

Question 52

critical angle is defined as __

Answer 52

incident angle for which refraction angle is 90 degrees

Question 53

what happens to the beam at the critical angle

Answer 53

refracted beam travels along interface

Question 54

common US artifacts

Answer 54

CARD - reverberation - dirty vs clean acoustic shadowing - acoustic enhancements - comet-tail artifacts

Question 55

reverberation occurs when ___

Answer 55

beam encounters 2 highly reflective surfaces

Question 56

acoustic shadowing occurs due to __

Answer 56

reduction in echo strength distal to high attenuating / reflective object

Question 57

what benefit does acoustic shadowing offer

Answer 57

visualize calcifications; often seen with bone & calcifications

Question 58

where does clean shadowing occur commonly

Answer 58

distal to larger calculi & bone as a dark anechoic band

Question 59

where does dirty shadowing occur commonly

Answer 59

distal to highly reflecting surface as multiple secondary reflections of low level echos that appear within the shadow

Question 60

comet tail artifacts appear as ___

Answer 60

multiple internal reflections within small reflective object producing many short tapered echoes

Question 61

energy loss during reverberation process causes echoes to ___

Answer 61

decrease in width & brightness