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Flashcards in SPI review 2 Deck (103):
1

attenuation coefficient and its units

the amount of attenuation per cm units dB/cm

2

attenuation cefficient is directly related to

frequency

3

attenuation coeff does not change when ________ changes

path length

4

in soft tissue attenuation coeff is approcimatley

1/2 the freqyency

5

mathmatical expression for attenuation coeff in soft tissue

0.5dB/cm/MHz

6

impedance

a number associated with a meduims resistance

calculated not measured

units are Rayls "Z"

7

acoustic impedance =

density x propagation speed

8

rayleigh scattering is =

freq to the 4th

9

oblique incidence

anything other than right angels

10

AKA normal incidence

perpendicular
orthogonal
right angel
ninety degrees

11

typical % of reflected intensity between soft tissue boundary

1%

12

% refelcted at air/tissue interface

99%

13

% reflected at bone/tissue interface

50%

14

refraction is

transmission with a bend

15

the physics of refraction is described by

snells law

16

refraction requirs _____ incidence

oblique (and diff speeds)

17

the angel of reflections is = to

the angle of incidence

18

which of the following best descrobes a refelction from a rough boundry?
non diffuse, absolute, rayleigh, smooth, non specular

non specular

19

the time of flight and and distance are ________ related

directly

20

range equation

distance to boundry = go return time x speed / 2

21

in soft tissue, every ____ of go return time means the reflector is ___ deeper in the body

13 micro sec
1cm

22

a property of certain material to create a voltage when pressure is applied or when the material is mechanically deformed

piezoelectric effect

23

materials deform or change shape when a voltage is applied to them

reverse piezoelectric effect

24

PZT AKA

ferroeclectric material

25

natural PZT

quartz, rochelle salts, tourmaline

26

man made PZT

barium titanate, lead metaniobate, lead titanate, lead zirconate titanate

27

temp PZT will depolarize at

360C* or 680F*

28

the complete destruction of all living microorganisms by heat, chemical agents, or radiation

sterilization

29

reduce infectious organisms

disinfection

30

thickness of PZT

1/2 wavelength thick

31

thickness of matching layer

1/4 wavelength thick

32

what is backing material made of

epoxy resin impregnated with tungsten

33

imaging transducer characteristics

damping

short pulse length and duration

low sensitivity

wide bankwidth

low Q factor

decreased output power

34

bandwidth

the range of frequencys from the highest to the lowest emitted from the transducer

35

bandwidth =

max freq - min freq

36

the process of _______ increases the range of freq in the bankwidth

backing material

37

main freq AKA

center

resonant

primary

natural freq

38

a unitless number representing the extent of damping

quality factor (Q factor)

39

the Q factor in typical imaging can be aprroximated by the number of _____ __ _______

cycles in the pulse

40

typical Q factor value

2-4

41

Q factor equation

Q = resonant freq/bandwidth

42

in pulsed wave transducers the main or center freq of the US pulsed transducer is determined by 2 characteristics of the crystal

thichness and prop speed

43

prop speed for PZT is approx

4-6mm/micro sec

44

in continouis wave trans the sound waves freq = the _______

freq of the voltage applied to the PZT by the machines electronics

45

when the PZT is 1/2 as thick the sounds freq is ____ __ _____

twice as high

46

the thinner the active element the _____ the freq

higher

47

the _________ the active materials prop speed the ________ the transducers freq

faster

higher

48

thin crystal and fast PZT =

higher freq

49

thick crystal and slow PZT =

lower freq

50

when a transducer is covered with gel on the inside, what can't it come into contact with in order to make the image? gel, water, talcum powder, sterile liquid, lubricating gel

talcum powder

51

t or f
if the freq of the electrical excitation voltage of a pulsed wave transducer is 6MHz, the main or ceter freq of the transducer is 6MHz

F

52

the impedance of a transducers active element is 1,900,000Z and for the skin is 1,400,000Z what is an acceptable impedance for the matching layer? 1,200,000Z, 1,400,000Z, 1,726,000Z, 1,950,000Z

1,726,000Z

53

T or F
the damping material improves the systems longitudinal res

T

54

narrow beams create ______ images

better

55

for unfocused continuous wave disc transducers, at the end of the near zone the beam diameter is __ the ________ _______

1/2
transducer diameter

56

at 2 near zone lengths, the beam diameter is ____ to the _______ -________

=

transducer diameter

57

two factors that determine focal depth (distance from tranducer to the focal point)

transducer diameter

freq of ultrasound

58

beams with a deep focas have a _____ ______ at the focus

lower intensity

59

shallow focus

small diameter

low freq

60

deep focus

large diameter

high freq

61

divergence is determinded by

transducer diameter

freq of ultrasound

62

in the far field, beam is narrow ________ res is the best with large diameter and high freq

lateral

63

in the far field, beam is wide where _______ res is worse, with small diameter and low freq

lateral

64

less divergence

narrower beam in far field

larger diameter active element

high freq

improved lateral res in far field

65

more divergence

wider beam in far field

small diameter active element

low freq

degraded lateral res in far field

66

v shaped wave

diffraction pattern
aka
huygens wavelet

67

huygens wavelet caused by

produced by a tiny source near the size of a wavelength, the waves will diverge in hour glass or V shage as they propagate

68

what happens in a huygens wavelet

each tiny part of transducer is individual source of sound. V shape is result of constructive and destructive interference of the many sound wavelets emitted from numerous soud sources.

69

a sound beam is created by a round PZT with a diameter of 10mm. The focal depth of the sound beam is 8cm. What is the diamter of the sound beam at a depth of 8cm? 8cm, 3mm, 5mm, 4mm

5mm

70

a sound beam is created by round pzt with a diameter of 10mm. The focal depth of the sound beam is 8cm. What is the diameter of the sound beam at a depth of 16cm? same as the trans diameter, 3/4 the trans diameter, 1/2 the transducer diameter, 4mm

the same as the transducer diameter

71

the ability to image accurately, not merely quality

resolution

72

the ability to distinguish two structures that are close to each other, front to back, paralley to, or along the beams main axis

axial resolution

73

axial res AKA

L longitudinal
A axial
R range, radial
D depth

74

units for axial res

distance

75

shorter pulses create ______ LARD res

shorter

76

can sonographer change LARD res

no, need new trans

77

T or F
a short pulse means a short spatial pulse length or a short pulse duation

T

78

when the LARD res is low the image accuracy is ________

superior

79

LARD equation

LARRD = spatial pulse length/2

80

typical LARRD value

0.05-0.5mm

81

LARRD soft tissue Equation

LARRD=0.77x # cycles in pulse/freq

82

LARRD is best with

less ringing (fewer cycles in pulse)

higher freq (shorter wavelength)

83

the minimum distance that 2 structures are separated by side to side, perpendicular to the sound beam that produces 2 distinct echoes

lateral res

84

lateral res AKA

L Lateral
A Angular
T Transverse
A Azimuthal

85

units of LATA

length

86

lateral res is = to

the beam diameter

87

since the beam diameter varies with _____ LARA res also vaies with _____

depth

88

lata res is best at

the focus or one near zone length (focal depth from the transducer because the sound beam is narrowest at that point

89

when 2 side by side structures are closer together than the beams width

only one wide reflection is seen on the image

90

why is LATA not as good as LARRD

US pulses are wider than they are short

91

LATA res is = to

beam diameter

92

high freq sound improves

LARRD everywhere in the image and LATA in the far field only

93

focusing alters beam in what ways

narrower waist in the US beam

shallower focus

smaller focal zone

94

focusing is effective in

the near field and focal zone

95

two types of focusing

fixed aka conventional or mechanical

adjustable by electronics aka phases array

96

phases array meand

adjustable or multi focusing

97

3 methods of focusing

lens
curved pzt
electronic focusing

98

lens

external focusing, distal to pzt

99

curved pzt

internal focusing

100

electronic focusing

adjustable, phased array
multy focusing

101

fixed focus have _____ lateral res

poor

102

an operation that lateral res of a given depth be estimated

measure the largest dimension on the image size of a point reflector

103

the more cycles there are in a pulse, the ______ is the numerical value of range res

greater