Ultrasound

Question 1

what is sound

Answer 1

it is the transfer of energy from one place to another via collisions between adjacent molecules. Vibrations pass through a transmission medium

Question 2

what is a wavelength

Answer 2

peak to peak

Question 3

what is the amplitude

Answer 3

wave displacement

Question 4

ultrasound info

Answer 4

• no IR or EM radiation
• 20 kHz +
• no adverse side effects
• visualises ST
• artefacts are recognisable
• direct contact is needed
• discriminates small differences between the structures

Question 5

what is frequency determined by?

Answer 5

rate of repetition of the original disturbance

Question 6

what does attenuation depend on?

Answer 6

frequency, medium and distance travelled

Question 7

what is a higher frequency linked to

Answer 7

higher attenuation

Question 8

what happens as sound passes through a medium

Answer 8

it becomes attenuated (scattered)

Question 9

what happens when the energy gets absorbed

Answer 9

intensity decreases

Question 10

what is refraction

Answer 10

a change in direction as they pass from one medium to another, accompanied by a change in WL and speed

Question 11

what is echolocation

Answer 11

it is the use of echoes to locate something, once it hits a material it is reflected back

Question 12

what does the pulse speed depend on

Answer 12

tissue type

Question 13

what is reflection

Answer 13

it is when a wave hits a medium boundary, the way is then reflected and transmitted. This is dependent on the dissimilarity of two media

Question 14

what is the piezoelectric effect

Answer 14

it is when a piezoelectric crystal is used which changes shape when a current is applied across it. The electricity current changes its shape as it oscillates when it sends an US pulse. A short pulse is directed as a narrow beam into the body the pulse reaches different tissues which are then reflected.

Question 15

how does US work

Answer 15

• transmits a sound wave into the body
• intensity of the reflected echoes are interpreted
• a handheld probe makes contact with the skin
• data is collected

Question 16

what does a transducer do?

Answer 16

it changes the signal from one form to another, an electrical signal -> sound and vice versa

Question 17

what does the transducer size and shape depend on?

Answer 17

accessibility
tissue depth
examined area

Question 18

how is an image formed

Answer 18

the sound emitted from the transducer is reflected from the patient back to the transducer

Question 19

what does a higher frequency result in

Answer 19

higher detail, less distance

Question 20

where does compression and rarefaction take place

Answer 20

compression = high pressure
rarefaction = low pressure

Question 21

how is the time taken for an echo to return determined

Answer 21

by the distance from the probe

Question 22

when does an interface occur

Answer 22

when there is change in density composition at which the sound passes through. This is a change in tissue between the boundary of the organ or fluid/gas

Question 23

what happens when the transducer receives a pulse

Answer 23

1. crystal changes shape to the US wave
2. an electrical current returns to the machine
3. image produced by the returning sound waves
4. produces the piezoelectric effect in reverse

Question 24

what is anechoic

Answer 24

without internal echoes
- echo free/poor
- echolucent

Question 25

what is echogenic

Answer 25

produces echoes
- echo rich
-hyperechoic

Question 26

what is hyper echoic

Answer 26

increased echoes compared to surrounding tissues
- echo dense

Question 27

what is isoechoic

Answer 27

same echogeneity as surrounding tissues

Question 28

what is hypo echoic

Answer 28

decreased echoes compared to surrounding tissues

Question 29

what is the scanning planes

Answer 29

-respect to the patient as well as the organ imaged