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Echocardiography > Physics > Flashcards

Physics Flashcards

1
Q

Specular reflectors are strong/weak? Scatterers are strong/weak reflectors?

A

Specular= strong Scatteres= weak

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2
Q

Does high frequency go with increased scatter?

A

Yes

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3
Q

another term for axial

A

longitudinal

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4
Q

what are the main variables affecting the following resolutions: 1) Longitudinal/axial- ? 2) Lateral-?

A

Longitudinal/axial = frequency (wavelength) Lateral= Beam width & Focus

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5
Q

what maneuver is helpful to eliminate near field (“Bang”) artifact?

A

contrast

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6
Q

if you see arcuate things on the echo, what artifact is it? (Physics II)

A

side-lobe

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7
Q

which variable determines the max depth imaged?

A

PRP (Pulse Repetition Period)

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8
Q
  • floats over the cardiac structures, won’t move with cardiac structures, due to PRP NAME THE ARTIFACT
A

Range Ambiguity Artifact

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9
Q

if the go-return time is 13 microseconds, what was the reflector depth? total distance travelled?

A

1cm deep in the body 2cm

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10
Q

in the artifact with the pleural effusion looking like it is floating in the middle of the LV, what was its name?

A

range ambiguity artifact. (change the depth to bring the effusion into the window and the LV then looks normal.)

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11
Q

name the artifact caused by mech valve that looks like a comet tail

A

reverberation artifact

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12
Q

are artifacts from low pressure gas bubbles better see with fundamental or harmonic imaging?

A

harmonic

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13
Q

v = f x ?

A

wavelength

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14
Q

wavelength of 3 MHz sound wave = ? in soft tissue

A

0.5 mm

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15
Q

a 3 dB change does what to intensity? how about 30dB?

A

doubles 1000 fold change (10^3): 30–> 10^3

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16
Q

what happens with high MI (>1) and low MI (

A

> 1 –> bubbles destroyed weak harmonic signals

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17
Q

eq’n for Acoustic Impedance (Z) what happens if Z very different b/w mediums (e.g. bone and soft tissue)?

A

Z = density x V - sound gets reflected (proportional to difference of Z’s SQUARED), not transmitted (V = velocity of sound)

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18
Q

What is relationship b/w acoustic impedance (Z) and % beam that is reflected?

A

difference of Z’s SQUARED

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19
Q

relationship b/w frequency and scattering

A

directly proportional

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20
Q

is diffraction greater with larger or smaller transducer?

A

smaller

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21
Q

the summation of losses due to reflection, scattering and absorption = ?

A

attenuation

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22
Q

what is the amount of attenuation in dB/cm/MHz in soft tissue?

A

1 dB/cm/MHz

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23
Q

most common Piezoelectric crystal used

A

PZT (lead zirconate titrate)

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24
Q

purpose of backing block in transducer

A

absorbs sound wave and limits ringing of crystal to allow for more discrete U/S pulse

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25
Q

purpose of matching layer in transducer

A

matches crystal to skin acoustic impedance to improve U/S transmission into tissues

26
Q

name the type of transducer that has CRYSTAL IMPURITIES, a BACKING BLOCK, and HARMONIC IMAGING

A

Wide Bandwidth transducer (Low Q-factor)

27
Q

for CW, would you use wide or narrow bandwidth transducer?

A

narrow

28
Q

time b/w transducer pulses = ?

A

PRP

29
Q

PRP’s relation to depth?

A

directly proportional

30
Q

PRF = ?

A

1/PRP

31
Q

definition of duty factor and values for CW and PW

A
  • fraction of PRP that emits sound CW = 1 , PW .001
32
Q

resolution along the length of the beam =?

A

axial resolution

33
Q

a 3MHz trasnducer has how much wavelength?

A

.5mm

34
Q

which resolution is determined by spatial pulse length?

A

axial

35
Q

(cycles x wavelength)/2 = ?

A

resolution

36
Q

how can you better separate fundamental and harmonic signal?

A

use longer pulse

37
Q

does a wider or narower beam improve lateral resolution?

A

narrow

38
Q

does higher frequency mean higher lateral resolution?

A

yes

39
Q

does higher frequency improve lateral AND axial resolution?

A

yes

40
Q

does amplification (“increasing gain”) effect the signal to npise ratio or contrast bubbles

A

no

41
Q

modified doppler eq’n

A
42
Q

nyquist limit (delta f) = ?

A

PRF/2

43
Q

the highest doppler shift that can be measured w/ pulsed doppler is called?

A

nyquist limit

44
Q

at what relative depths and frequencies can you measure higher velocities?

A

shallower depth, lower frequencies

45
Q

is COlor Flow Imaging CW or PW?

A

PW

46
Q

what will more pulses with color flow imaging do to frame rate?

A

make it slower

47
Q

Z/PRP = ?

(Z = distance)

A

velocity

48
Q

Eq’n for Duty Factor

A

Pulse Duration/PRP = DF

49
Q

for every 3dB attenuation, how much reduciton in intensity is there? what about for 10dB attenuation?

A

3dB–> 1/2

10dB–> 1/10

50
Q
A

D

51
Q

the frequency range for audible sound? U/S?

A

20Hz-20kHz

(U/S > 20kHz)

52
Q
A

B: Frame rate

53
Q

4 ways to improve temporal resolution

A

DECREASE: depth, width, #focal points, line density

54
Q
A

D- speed of sound always 1540 m/s

55
Q

will increasing gain increase output power? what will inc output power?

A

no. M.I.

56
Q

In soft tissue, every 13 microsecond of go-return time means the reflector is _cm deep in body?

A

1

57
Q

recite the 13 microsecond table

A
58
Q

lateral resolution is dependent on the ___ of the ultrasound beam?

A

width

59
Q

PRF =?

A

PRF = 77,000/depth

60
Q

modified doppler velocity equation from physics lecture

A

Echocardiography (29 decks)

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