Introduction and Physics

Question 1

what is an ultrasound?

Answer 1

sound with a frequency higher than human hearing can detect

Question 2

what is velocity in soft tissue?

Answer 2

1540 m/s
constant

Question 3

what is used to produce ultrasound?

Answer 3

piezoelectric crystals
electric charge

Question 4

what is axial resolution useful for?

Answer 4

differentiating structures parallel to ultrasound beam

Question 5

what is lateral resolution useful for?

Answer 5

differentiating structures perpendicular to ultrasound beam

Question 6

what is elevational resolution?

Answer 6

third dimension of ultrasound beam
slice thickness

Question 7

what happens to the wave the deeper it travels?

Answer 7

it becomes weaker
0.5 dB/cm/MHz

Question 8

what is the ultrasound image formed by?

Answer 8

returning echos

Question 9

what does the angle of incidence between the ultrasound beam and the direction of flow need to be?

Answer 9

<60 degrees

Question 10

does power doppler provide direction or velocity?

Answer 10

no

Question 11

what is power doppler best for?

Answer 11

small vessels
amount and presence of flow

Question 12

what are the doppler modes?

Answer 12

power doppler
color doppler
spectral doppler

Question 13

what are the basic ultrasound machine controls?

Answer 13

gain
frequency
depth
beam size
focal point

Question 14

what does increasing the frequency do?

Answer 14

decreases depth
increases resolution

Question 15

what is the focal point for?

Answer 15

maximal lateral resolution

Question 16

what is anechoic?

Answer 16

black echogenicity

Question 17

what are the options for echotexture?

Answer 17

heterogenous
homogenous

Question 18

what is a comet tail?

Answer 18

special form of reverberation artifact
with gas

Question 19

what is acoustic shadowing?

Answer 19

ultrasound beam almost completely reflected or absorbed
mineral or gas

Question 20

what is posterior enhancement?

Answer 20

behind pure fluid
almost no ultrasound beam attenuation through fluid

Question 21

what is edge-shadowing?

Answer 21

form of refraction artifact
rounded structures

Question 22

what is the frequency of ultrasound?

Answer 22

> 20,000 cycles/sec
20 kHz

Question 23

what is frequency?

Answer 23

cycles/sec
Hz

Question 24

what is the equation for velocity?

Answer 24

velocity = frequency x wavelength

Question 25

what does an increase in frequency lead to?

Answer 25

decrease in wavelength
less depth, more resolution

Question 26

what determines axial resolution?

Answer 26

pulse length

Question 27

what determines lateral resolution?

Answer 27

beam width
adjusting focal point

Question 28

what determines elevational resolution?

Answer 28

beam thickness

Question 29

what is the equation for acoustic impedance?

Answer 29

acoustic impedance = velocity (1540m/s) x tissue density

Question 30

what happens to the majority of ultrasound transmitted through tissue?

Answer 30

it is absorbed
convert into heat

Question 31

what do the colors in color doppler signify?

Answer 31

direction of flow

Question 32

what is gain?

Answer 32

increase signal of returning echoes

Question 33

what happens when you increase the frequency?

Answer 33

depth is decreased
resolution is increased

Question 34

how is the probe marker oriented when scanning a dog?

Answer 34

cranial in longitudinal plane
to the right in transverse plane

Question 35

what is reverberation artifact from?

Answer 35

gas

Question 36

when is a mirror image seen?

Answer 36

strong reflector
diaphragm