Ultrasound

Question 1

What is ultrasound?

Answer 1

1 ) A procedure that uses high frequency sound waves to produce images of internal organs or the interior of the body

2) works similar to sonar tech or echolocation in animals

Question 2

At what frequencies does ultrasound work at?

Answer 2

> 20,000Hz (20kHz)

Question 3

How should you measure wave lengths?

Answer 3

1) peak-to-peak

OR

2) trough-to-trough

Question 4

What is soft tissue propagation?

Answer 4

1) how fast the sound wave travels through soft tissue
2) speed is 1540 m/s and can’t be altered
3) can change the frequency to change the sound wave

Question 5

What is reflection as it relates to ultrasound?

Answer 5

1) it is when the sound waves produced by the transducer hit an object and come back
2) it occurs between two tissues with very different acoustic impedances

Question 6

What is specular reflection?

Answer 6

1) when sound waves encouter tissue boundaries that are large and smooth it reflects back in a uniform way

Question 7

What is backscatter as it relates to ultrasound?

Answer 7

1) a type of reflection
2) occurs on rough surface and small structures
3) no uniform way to reflect

Question 8

What is attentuation as it relates to ultra sound?

Answer 8

1) is the absorption of energy to the body
2) sound energy is converted to heat
3) results from specular reflection and backscatter

Question 9

What is refraction as it relates to ultrasound?

Answer 9

1) refraction is the bending (changing direction) of a sound wave as it encounters an interface between two materials with different speeds of sound
2) can lead to artifacts

Question 10

Why is ultrasound gel used?

Answer 10

1) it allows ultrasound waves to penetrate the body from the transducer
2) reduces reflection and refraction (waves travel better through water than air)
3) without it less than 1% of the signal goes into patient, 99% with it

Question 11

How does a transducer work?

Answer 11

1) it converts electrical energry into mechanical energy
2) uses piezoelectric effect
3) it then sends out a signal which comes back and causes the crystals to vibrate

Question 12

What are some properties of a curved tranducer? What whould it be used for?

Answer 12

1) it can penetrate deeply (up to 30cm)
2) uses low frequency
3) ex: abdominal aorta

Question 13

What are some properties of a linear tranducer? What whould it be used for?

Answer 13

1) can’t scan deeply (8-10cm) so superficial structures
2) high frequency
3) ex: duplex carotid

Question 14

What are some properties of a phased array tranducer? What whould it be used for?

Answer 14

1) goes deeper (30cm)
2) low frequency
3) it is smaller in size
4) ex: heart examinations

Question 15

What is lateral resolution?

Answer 15

1) the ability to distinguish objects that are side-by-side

2) narrower the beam, the better the resolution

Question 16

What is axial resolution?

Answer 16

1) ability to distinguish two objects that are longitudinally adjacent
2) higher frequency means better axial resolution

Question 17

How is the doppler effect used in ultra sound?

Answer 17

1) it can be used to asess the flow of blood
2) red blood cells move towards the transducer = high frequency
3) red blood cells move away from the transducer = low frequency

Question 18

What is pulsed-wave (PW) doppler?

Answer 18

1) measures blood flow velocity at one specific location
2) sends a signal and wait to receive a signal back
3) used with a curved transducer
4) low velocities

Question 19

What it continuous wave (CW) doppler?

Answer 19

1) there are two crystals working simultaneously
2) one always sends and one always receives
3) measures high velocities
4) obtains the signal along the entire length of the ultrasound beam

Question 20

What is colour flow Doppler?

Answer 20

1) is a visualisation of flow direction and velocity within a user defined area
2) BART = Blue Away, Red Towards

Question 21

What are image artefacts?

Answer 21

Imaging artefacts are incorrect representations of anatomy or function

Question 22

What is reverberation?

Answer 22

1) images artifact
2) ultrasound beam bounces several times between two strong specular reflectors
3) takes longer for the signal to return so machine misinterprets the info

Question 23

What is acoustic shadowing?

Answer 23

1) image artefact
2) highly echo reflective structure that blocks the ultrasound from penetrating
3) can’t see under the shadow

Question 24

What is a shadow artifact?

Answer 24

1) ultrasound beam encounters a strong reflector and the energy of the forward beam becomes degraded = blocked signal
2) can fix by angling in with different waves

Question 25

What is beam width artifact?

Answer 25

1) something from the edge of the image but the machine “thinks” is from the center

Question 26

How can you minimize risks during an ultrasound?

Answer 26

1) only perform ultrasound for appropriate clinical indications
2) keep power output as low as possible
3) keep exposure time to a minimum
4) M-mode and 2D have the lowest intensity, PW doppler has the highest, colour doppler in the middle
5) check for risk of electric shock
6) injury risk with trips and falls
7) risk of infection