ultrasound

Question 1

sound is what type of energy

Answer 1

mechanical

Question 2

what is required for the propagation of sound waves

Answer 2

a medium

Question 3

frequency of wave =

Answer 3

number of cycles per sec
aka Hz

Question 4

humans can detect sound in what range

Answer 4

20-20,000 Hz

Question 5

ultrasound threshold

Answer 5

> 20,000 Hz

Question 6

medical ultrasound uses what level

Answer 6

2-15 MHz
2,000,000 - 15,000,000Hz

Question 7

wavelength is represented by what

Answer 7

λ

Question 8

what is wavelength

Answer 8

distance between the same point on subsequent waves

Question 9

what is amp

Answer 9

heigh tof crest or trough
E power of the wave

Question 10

frequency and wavelength are ___ proportional

Answer 10

inversely

Question 11

increasing freq does what to axial resolution

Answer 11

improves it

Question 12

structures less than one wavelength part look

Answer 12

mashed together

Question 13

structures one or more wavelengths apart look

Answer 13

separate and more clear

Question 14

what is propagation

Answer 14

when a source vibrates, it transfers energy to the surrounding particles, causing them to vibrate

Question 15

propagation requires what

Answer 15

an elastic medium

Question 16

what is compression

Answer 16

molecules are force or pressed together

Question 17

what is rarefaction

Answer 17

molecules are given extra space and allowed to expand

Question 18

as molecules compress, they …

Answer 18

pass kinetic energy to each other

Question 19

acoutstic velocity is what

Answer 19

(c) the speed at which a wave propagates through a medium

Question 20

λ = ?

Answer 20

c / f

Question 21

acoustic velocity is __ in most soft tissue

Answer 21

1540 m/s

Question 22

what are the 3 acoustic velocity determinants

Answer 22

1. density
2. compressibility
3. rigidity/stiffness

Question 23

ρ

Answer 23

density
greater ρ, the more it impedes sound

Question 24

K

Answer 24

compressibility
volume dec when pressure
easy to reduce vol = greater compressibility

Question 25

B

Answer 25

rigidity/ stiffness the stiffer, the faster sound moves through

Question 26

which acoustic velocity determinants does NOT have an inverse relationship

Answer 26

B rigidity/stffness

Question 27

what c determinant has the least effect

Answer 27

density ρ

Question 28

sound travels (faster/slower) in solids

Answer 28

faster more dense, but less crompressible

Question 29

at what speed does sound travel in soft tissue?

Answer 29

c = 1540 m/s

Question 30

what is the formula for the echo range principle

Answer 30

speed = distance/time distance = speed /time

Question 31

what is pulse repetition frequency

Answer 31

of pulses emiited per time

Question 32

what is the piezolelectric effect

Answer 32

pressure wave incident on crystal, causes vibrations; causes electronic effect

Question 33

transmission gain does what

Answer 33

modulates the voltage applied to the crystal

Question 34

increasing transmission gain = ? signal

Answer 34

stronger transmitted signal

Question 35

what is the reverse piezolelectric effect

Answer 35

charge is applied to a piezoelectric crystal, it vibrates; creates pressure mechanical wave

Question 36

intensity is what

Answer 36

rate at which E is transmitted by the sound wave, over a small area

Question 37

increasing intensity does what

Answer 37

inc oscillation of particles max particle velocity increases

Question 38

Z represents what

Answer 38

acoustic impedance

Question 39

what is acoustic impedence

Answer 39

Z how much resistance an ultrasound beam encounters as it passes through tissue

Question 40

Z = ?

Answer 40

ρ x c

Question 41

what are the 4 interactions of acoustic waves with tissue

Answer 41

reflection scatter refraction absorption

Question 42

reflection happens when

Answer 42

there is a high difference in Z of the tissues

Question 43

reflection fraction formula

Answer 43

(Z2 - Z1 / Z2 + Z1) ^2

Question 44

if the transmitted wave is Z2 = ρ2 c2, then what is the reflected wave

Answer 44

Z2 = ρ1 c1

Question 45

what are P1, P2, and P3

Answer 45

incident wave reflected wave transmitted wave

Question 46

percent reflectivity formula

Answer 46

%R = (Z2 – Z1/Z2 + Z1)2 x100 aka Rfraction x 100

Question 47

percent transmission formula

Answer 47

%T = 100 - %R

Question 48

on what type of surface does specular reflection occur

Answer 48

large, smooth surfaces ie one

Question 49

what is specular reflection

Answer 49

sound reflects in a single direction

Question 50

what does i = r mean

Answer 50

(specular reflection) the angle of incidence is the same as the angle of reflection

Question 51

what does specular reflection provide the US image

Answer 51

boundary or edge detail

Question 52

what is shown well here

Answer 52

boundary or edge detail

Question 53

what is the issue with specular reflection

Answer 53

it is angled away from the transducer so transducer has to be parallel to specular surface or interface

Question 54

if tissue boundary width is less than wavelength

Answer 54

the wave will not be refelcted

Question 55

air between the skin causes what

Answer 55

99.9% refelction why gel is used

Question 56

air and soft tissue %R

Answer 56

99.9

Question 57

fat and soft tissue %R

Answer 57

0.032

Question 58

water and soft tissue %R

Answer 58

0.427

Question 59

bone and soft tissue %R

Answer 59

43%

Question 60

what is a mirror image artifact

Answer 60

- primary beam reflected form a highly reflectiv surface (ie diaphragm) - hits something elses and reflects back to diaphragm - reflects back to transducer

Question 61

what is shown here

Answer 61

mirror image artifact

Question 62

soft tissue is what type of reflector

Answer 62

a diffuse reflector

Question 63

most echos are from

Answer 63

scattering

Question 64

what are these 2 interactions

Answer 64

specular reflection diffuse reflectionwh

Question 65

what is refraction

Answer 65

change in direction when crossing a boundary between 2 media w diff speeds of sound

Question 66

no refraction happens when angle of incidence is

Answer 66

90 deg

Question 67

what is the determination of which way refraction goes

Answer 67

C1 > C2 toward normal C2 < C1 away from normal

Question 68

what artifact is here

Answer 68

refraction and misregistration artifact

Question 69

what is the basis concept of tx us

Answer 69

as us waves pass through tissue, orderly vibrational E is converted into random vibrational heat energy

Question 70

relate frequency to absorption

Answer 70

high freq = more rapid attenuation

Question 71

what is shown here

Answer 71

posterior acoustic enhancement

Question 72

what is here

Answer 72

acoustic shadowing

Question 73

what is TGC

Answer 73

time gain compensation electronically amplifies the signal as a fn of depth

Question 74

how is TGC done

Answer 74

with time compensation sliders

Question 75

how are sagittal images done

Answer 75

green light up (H)

Question 76

how are transverse images done

Answer 76

green light right

Question 77

what are the 4 categories of echogenicity

Answer 77

hyperechoic isoechoic hypoechoic anechoic

Question 78

what is hyperechoic

Answer 78

bone

Question 79

what is isoechoic

Answer 79

liver, kidneys, muscle

Question 80

what is hypoechoic

Answer 80

fat and blood

Question 81

what is anechoic

Answer 81

fluid filled cysts

Question 82

what tx procedure uses ultrasound to guide?

Answer 82

ultrasound guided venipuncture