Ultrasound

Question 1

What is sound?

Answer 1

A result of mechanical energy producing alternating compression and rarefaction of the conducting medium

Question 2

What is the unit of frequency?

Answer 2

Hertz (Hz)

Question 3

What range of frequencies can humans hear?

Answer 3

20 Hz to 20 kHz

Question 4

What is the frequency of ultrasound waves?

Answer 4

Greater than 20kHz

Question 5

How do diagnostic ultrasound machines work?

Answer 5

Uses short sound pulses that are transmitted into the body
These can be reflected, scattered, refracted or absorbed
The combine effects of this causes attenuation in the intensity of the sound pulse as it travels
This allows the machine to distinguish between different tissues and create an image

Question 6

What are the advantages of ultrasound?

Answer 6

Ultrasound is safe
No ionizing radiation
Equipment is portable and inexpensive

Question 7

What are the disadvantaged of ultrasound?

Answer 7

Highly operator dependent
Structures around bone do not give clinically useful images
The attenuation of the ultrasound signal at air/tissue boundaries means it is unsuitable for imaging structures obscured by gas

Question 8

What are the different components of an ultrasound machine?

Answer 8

Monitor
US unit- signals are processed
Control panel
Transducers
Data storage device

Question 9

What are the main parts of the transducer?

Answer 9

Electrodes applying an alternating potential difference
Piezoelectric crystal
Plastic nose
Backing block
Acoustic insulator

Question 10

What are piezoelectric crystals?

Answer 10

Ceramic crystals that deform and vibrate when they are electronically stimulated

Question 11

How do piezoelectric crystals work?

Answer 11

Echoes distort the crystals and generate an electric pulse to create an image

High-amplitude echoes produce greater crystal deformation and generate a larger electronic voltage

Question 12

What are the different types of transducers?

Answer 12

Convex array
Micro-convex array
Linear array
Endovaginal and rectal array

Question 13

Describe linear-array transducers

Answer 13

Images obtained with linear arrays always have a flat superficial surface

Often very high frequency so can only be used for superficial tissues

Question 14

Describe curved-array transducers

Answer 14

The surface is curved creating a convex shape

Those with short radi can be used for endoluminal scanning

Those with larger radi can be used for abdomen scanning

Question 15

Describe phased-array transducers

Answer 15

Every element in the array participates in the formation of the pulse

Because the sound beams are steered at varying angles from one side to the other, sector images are produced

Question 16

Describe intraluminal probes

Answer 16

Small transducers that can be placed within body lumens

Can be positioned closer to the organ so a higher resolution image can be obtained

Very small transducers have been added to flexible endoscopes to scan and guide biopsies in the gastrointestinal tract

Question 17

What is A-mode imaging?

Answer 17

A method of displaying echoes acquired in 1 dimension.

Depth is represented along 1 axis and the echo amplitude is displayed along a perpendicular axis

Question 18

What is B-mode imaging?

Answer 18

Brightness is the most commonly US mode

The brightness of the dot represents the amplitude of the returning signal

The position of the dot represents the depth from which the signal is returning and depends on the round-trip time of the US signal

Multiple scan lines across a plane are combined to produce a 2D image

Question 19

What do the colours black, white and grey represent in a B-mode US?

Answer 19

Black- anechoic fluid
Dark grey- pus in an abscess
White-bone
Grey- organs and tissue

Question 20

What are the different types of Doppler US?

Answer 20

Colour
Power colour
Pulsed

Question 21

Describe colour doppler US

Answer 21

Measures and colour codes the direction and magnitude of the mean doppler frequency shifts that occur in moving red blood cells and superimposes a colour depiction of these data on the gray-scale image

Question 22

Describe power colour doppler US

Answer 22

Depicts the amplitude or power of the doppler signals. This allows better sensitivity for the visualisation of small vessels, but at the expense of directional information

Question 23

Describe pulsed doppler US

Answer 23

Allows a sampling volume to be positioned in a vessel visualised on the gray-scale image and displays a spectrum of the full range of blood velocities within the gate plotted as a function of time

Question 24

Describe M-mode US

Answer 24

Designed to document and analyze tissue motion

Uses a line from the 2D scan- reflections from this line are displayed in a graphic form

Motion on vertical axis, time on the horizontal axis

Important for studying cardiac valve

Question 25

Describe 3D US

Answer 25

Data is accquired as a stack of parallel cross sections with the use of 2D scanner Can be displayed as multiplanar reformatting, surface rendering, volume rendering and virtual endoscopy

Question 26

What frequency setting is resolution?

Answer 26

Highest

Question 27

What frequency setting is penetration?

Answer 27

Lowest

Question 28

What frequency setting is general?

Answer 28

Intermediate frequency

Question 29

What is the gain control?

Answer 29

Adjusts amplification of the returning acoustic signals Too little produces a dark image Too much produces a white image

Question 30

What sort of presets would be present on a US machine?

Answer 30

Vascular, breast, nerve, muscoskeletal

Question 31

Describe acoustic enhancment

Answer 31

Only a small amount of energy will be absorbed by some fluids, meaning the tissues behind will be shown in a greater depth

Question 32

What are the 4 manipulation manoeuvers?

Answer 32

Pressure Alignment Rotation Tilt

Question 33

What angle would you position the transducer?

Answer 33

At 90 degrees to the structure of interest

Question 34

What is ansiotropy?

Answer 34

An artefact encountered when the US incorrectly diagnoses a tendon tear

Question 35

How does ansiotropy happen?

Answer 35

Changing the angle when examining the tendon will change the colour from hyperechoic to hypoechoic. When seeing hypoechoic it is easy to misdiagnose tendinosis

Question 36

What is lithotripsy?

Answer 36

Stones present in the urinary system are crushed by the vibrating impulses of the ultrasound machine

Question 37

What is cavitation?

Answer 37

When the US produces small pockets of gas in the tissue

Question 38

What are the Thermal index (TI) and Mechanical Index (TI) used for?

Answer 38

Provides operator with an indication of the potential for ultrasound induced bio-effects

Question 39

What is the acronym ALARA?

Answer 39

As Low As Reasonably Achievable

Question 40

What value should you keep the TI and MI under?

Answer 40

1

Question 41

What is point-of-care ultrasound (POCUS)?

Answer 41

Defined as a goal-directed, bedside US examination to answer a specific diagnostic question or to guide performance of an invasive procedure

Question 42

How does US help vascular access?

Answer 42

Guides the needle/cannular allowing the health professional to see the object enter the patients vein, in both transverse and cranial planes

Question 43

How does the angle of incidence effect the resolution of the image?

Answer 43

If perpendicular more waves will be reflected back to the transducer resulting in a better image If the wave are more parallel the waves will be scattered and create a worse image

Question 44

How can you assess the hip stability of newborns?

Answer 44

A transverse scan of the hip while in flexion

Question 45

Describe a benign breast lump

Answer 45

``` Oval shaped Wider than deep SMooth Variable to hyperechogenicity Uniform homogeneity of internal echoes ```

Question 46

Describe a malignant breast lump

Answer 46

``` Variable in shape Deeper than wide Irregular or spiculated Low-level echotexture Absent lateral shadowing Attentuation with obscured posterior margin Calcification Microlobulation Intraductal extension Infliltration across tissue planes ```

Question 47

What does the acronym FAST stand for?

Answer 47

Focused Assessment with Sonography in Trauma

Question 48

What is FAST used for?

Answer 48

Performed in the emergency department to assess patients admitted with blunt abdominal trauma