Ultrasound 1

Question 1

Describe how a diagnostic ultrasound works

Answer 1

• It uses short sound pulses that are transmitted into the body.
• The pulses can then be reflected, scattered, refracted or absorbed.
• These effects result in the attenuation in the intensity of the sound pulses which limits the depth of imaging.

Question 2

Describe some of the advantages of ultrasounds

Answer 2

• Safe
• No ionising energy
• Equipment is compact, portable and relatively inexpensive.

Question 3

Describe some of the disadvantages to ultrasounds

Answer 3

• highly operator dependant
• Structures surrounded by bone cannot be imaged
• Attenuation of ultrasound at air/tissue boundaries means it is not suitable to image structures such as the lung and organs obscured by overlying bowel.

Question 4

How is ultrasound produced and detected?

Answer 4

By using an ultrasound transducer. They are capable of sending an ultrasound and detect the sound bounced back and convert it to an electrical signal.

Question 5

What are the crystals in an ultrasound and what are they used for?

Answer 5

They are ceramic crystals that deform and vibrate when they are electrically stimulated and generate the sound pulses.

Question 6

Name the three main types of transducer/probes and another common probe.

Answer 6

Linear array probe,
Curved array probe
Phased array probe.
An intraluminal probe is also common

Question 7

Describe some of the features of the linear -array probe

Answer 7

Uses high frequency which doesn’t penetrate deep tissues so it only used to image superficial structures.D

Question 8

Describe some of the features of the curved array probe

Answer 8

-The curved head gives an extended field of view and is used general abdomen and obstetrical scanning.

Question 9

Describe a feature of the phased-array probe

Answer 9

The probe is smaller and therefore used for scanning areas such as between the ribs. Where acoustic access is limited.

Question 10

Describe some of the features of intraluminal probe

Answer 10

• Can be places close to the organ of interest so higher frequencies can be used therefore receiving a higher resolution image.
• Avoids shadowing from adipose tissue and bowel gas.
• Produces images of much higher quality

Question 11

Describe some of the modes of scanning

Answer 11

• A-mode imaging (displays echos)
• B-Mode (two dimension mode, it is most commonly used. The spike is converted to a dot and the brightness of the dot represents the amplitude of returning signal.
• M-mode (used to analyse tissue movement, important when looking at cardiac valves)
• 3D US imaging (used in gynaecology and foetal anatomy)

Question 12

What is echogenicity?

Answer 12

The ability to bounce an echo

Question 13

Describe the different colours produced in ultrasound

Answer 13

Isoechoic - very light grey. Usually very dense structures like tissue
Hypoechoic - Darker grey. Can be pus
Hyperechoic - White. Can be bone, stones and metallic objects
Anechoic - black. Can be fluid (blood, urine and cysts) and pus

Question 14

Describe the different types of Doppler ultrasound

Answer 14

Colour Doppler - Measures and colour codes the direction and magnitude of Doppler frequency shifts that occur in moving red blood cells. Blood moving towards the probe is red, blood moving away from the probe is blue (BART)
Power colour Doppler - Allows for better sensitivity for visualisation of small vessels but at the expense of directional information.
Pulsed Doppler - Measures blood velocity

Question 15

What does gain control?

Answer 15

The brightness of the screen. Increased gain will brighten. Decreased gain will darken.

Question 16

Name some ultrasound artefacts

Answer 16

Acoustic Enhancement - occurs deep to a fluid filled structure, the area will appear much brighter.
Anisotrophy - Important in musculoskeletal, occurs due to poorly positioned probe. Can lead to false diagnosis.