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Flashcards in Ultrasound Deck (18)
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1
Q

What is the frequency of medical US?

A

2-20 milllion Hz

2
Q

What is the transducer?

A

Contains piezo-electric crystal

Converts energy from electrical to acoustic

3
Q

What frequencies do transducers come in + what are they good for?

A

High (7-18) - high resolution but low depth, good for superficial vessels

Low (2-6) - penetrate deeper but lower resolution eg abdo + obstetric

4
Q

What is acoustic impedence?

A

Property of each tissue - depends on density + speed of sound waves passing through it

5
Q

What is shadowing?

A

Calcium is a strong reflector so causes shadowing posteriorly (eg in gallstones)

6
Q

What do vessels, bones, soft tissue, nerves + muscle look like + what terminology do we use to describe it?

A

Vessels - black - anechoic

Bones - white - hyperechoic

Soft tissue - grey - isoechoic

Nerves - honeycomb - hypo/hyperechoic

Muscle - gray - isoechoic with white strands

7
Q

How to alter depth + why

A

Start with high depth then decrease to put area of interest around 3/4 of screen depth

8
Q

What is gain compensation?

A

Selectively amplifying echoes from deep tissues

9
Q

What are calipers used for?

A

Allows measures to be made

10
Q

What are the commonly seen artefacts?

A

Shadowing

Acoustic enhancement

Reverberation

Comet tail

11
Q

What is shadowing?

A

Strong reflective region of calcium that reduce energy remaining in beam distal to it

12
Q

What is acoustic enhancement?

A

Occurs when sound waves pass through low acoustic impedance to normal acoustic impedance

Occurs in vessels, bladder, cysts

13
Q

What is reverberation?

A

Large echo created by strong reflector - bounces back after hitting probe

Continues to bounce back and forth giving impression of multiple lines - equally spaces + gradually losing brightness

14
Q

What is a comet tail artefact?

A

multiple reflections occur within small strongly reflecting object

15
Q

What is a FAST scan?

A

Focussed assessment with sonography for trauma

Checks for fluid/ air in pericardial, peritoneal + pleural cavity

16
Q

Where are the probes placed in a FAST scan?

A

Subcostal cardiac

RUQ

LUQ

Pelvis

17
Q

What is static vs dynamic US access?

A

Static = mapping

Dynamic = views needle in real time

18
Q

How to US aorta

A

Put probe transverse across body

Push down to move bowel, aorta will appear cross sectionally, verterbra posteriorly

Measure using calipers the diameter

Turn probe longitudinally to measure diameter again

Transverse, measure down to the bifurcation