Ultrasound

Question 1

What EMR is used in Ultrasound?

Answer 1

N/A soundwaves are used

Question 2

What is ultrasound?

Answer 2

High-frequency sound waves beyond the range of human hearing (20Hz-20 kilohertz)

Question 3

What is the diagnostic ultrasound frequency?

Answer 3

1-30megaHz

Question 4

Advantages of ultrasound

Answer 4

No ionising radiation
Well-tolerated
Relatively cheap
Readily available
Real-time
Portable

Patient not suitable to CT / MRI
Claustrophobic / poor renal function / metallic objects

Question 5

Limitations of ultrasound

Answer 5

Operator dependent
Bowel gas
Obesity
Bone
Good sensitivity but not always specific

Question 6

What does the transducer do

Answer 6

Both send and detect the echo

Sends loads of beams of sound (FOV)

Question 7

Piezoelectric crystal

Answer 7

You give current to the crystals and the crystals start to vibrate and this vibration produces sound.
Electrical to mechanical
Its an alternating current

Then the sounds echo back from the structures and goes back to the transducer
This distorts the crystals (mechanical to electrical) to produce the image.

The electrical signals are processed and stored on a computer memory.

Question 8

What is amplitude?

Answer 8

Loudness dB

Question 9

What is high frequency used for?

Answer 9

Higher frequency has a shorter wavelength gives greater resolution

BUT…… poorer penetration because it is preferentially absorbed

Good image detail but poor for scanning deep structures

Question 10

What is low frequency used for?

Answer 10

Lower ultrasound frequencies have a longer wavelength so give better scanning at depth but lower resolution

Reduced image detail but can scan deeper structures

Question 11

Types of probes

Answer 11

Curvilinear
Linear
Phased array
Intra-cavity probes

Question 12

Echogenicity

Answer 12

tissues that are capable of producing echoes of different strength depending on their acoustic impedance.

Sound travels through tissue at different rates depending on it acoustic impedance.

Question 13

Anechoic

Answer 13

no reflected echoes (black area)

Question 14

Homogeneous

Answer 14

Same densities/similar

same grey

Question 15

Heterogenous

Answer 15

Different densities

Lots of different echo

Question 16

Hyperechoic

Answer 16

Brighter than normal tissues

Question 17

Hypoechoic

Answer 17

Darker than normal tissues

Question 18

Focal area describe

Answer 18

Well-defined - easy to see

Poorly defined - hard to see

Question 19

Simple cyst

Answer 19

Same density throughout it

Question 20

Complex cyst

Answer 20

different densities throughout it

Question 21

Acoustic shadowing

Answer 21

causes shadow appearance on image, soundwave doesnt travel through certain things like bones, gallstones

Question 22

Acoustic enhancement

Answer 22

Soundwave travels through the tissue more easily and causes a light
less of the beam is sent back/absorbed by the tissue.

Question 23

What is the risk with ultrasound?

Answer 23

High output can cause heating

More risk to sensitive organs such as foetal

Question 24

Safety Indices

Answer 24

MI  = mechanical index
TIB = Thermal index for bone > 10 weeks gestational age
TIS = Thermal index for soft tissue < 10 weeks gestational age
TIC = transcranial imaging