Ultrasound

Question 1

What are the basic ultrasound principles?

Answer 1

• Uses transmission of sound waves through tissue to produce an image
• Current is applied to the piezo-elements in the transducer
• Cuases the crystals to change shape and oscillate, producing an ultrasound wave
• returning sound waves are received at the transducer, causing compression of the crystals and thus an electric voltage
• The signal is then amplified, converted and dispalyed as a dot on the screen

Question 2

What is Reflection?

Answer 2

A wave is reflected back to the transducer and called an echo

Question 3

What is refraction?

Answer 3

The change in direction of a wave due to differing velocities of tissues

Question 4

What is diffraction?

Answer 4

change in the direction of a wave through an opening or a barrier, allows sound waves to be detected

Question 5

What is attenuation?

Answer 5

Loss of energy of a wave due to scatter or absorption

Question 6

What is a linear array probe?

Answer 6

• Crystals in a line
• Rectangular image
• No near field artefact
• Large footprint

Question 7

What is a curved probe?

Answer 7

• Crystals are in a curve
• Fan shaped image
• Near field artefact
• Smaller footprint

Question 8

What is a phased array probe?

Answer 8

• Crystals in a line
• Fan shape- greater depth
• Steered electronically
• Smaller footprint

Question 9

What is a high frequency ultrasound?

Answer 9

• Good axial resolution
• More rapid beam attenuation
• Poor penetration

Question 10

What is axial resolution?

Answer 10

The ability to determine two points along the path of the beam

Question 11

What is the definition of gain?

Answer 11

Changes the overall brightness of the image

Question 12

What is time gain compensation?

Answer 12

• Echoes from deeper tissues are
  weaker due to attenuation
• TGC controls brightness at
  different levels though the tissue

Question 13

What is the focal zone?

Answer 13

• Area where the image is optimised by focusing the soundwave
• Most often shown by a triangular marker
• Keeps teh region interest in the focal zone
• Improves lateral resolution

Question 14

What does reverbation cause?

Answer 14

Parrallel bright lines

Question 15

What does mirror image cause?

Answer 15

occurs at the curved reflective surface

Question 16

What is acoustic enhancement caused by?

Answer 16

Lack of attenuation

Question 17

What is poor probe contact caused by?

Answer 17

Insufficient clipping or not enough gel

Question 18

what is acoustic shadowing

Answer 18

If meet highly reflective interface get
complete reflection and distal shadow

Question 19

what is edge shadowing

Answer 19

distal to lateral aspect cystic structure

Question 20

what is slice thickness

Answer 20

part of the beam is wider than a cystic structure

Question 21

When may you do an elective abdominal ultrasound?

Answer 21

• Any condition involving an abdominal organ
• Identifying and describing abdominal tumours
• Staging of neoplasia
• Intra-abdominal biopsy
• System-Specific Investigation, e.g repro tract

Question 22

What is an emergency abdo ultrasound called?

Answer 22

POCUS scan

Question 23

What are the benefits of an abdominal ultrasound?

Answer 23

• Non-invasive and safe
• Anaesthesia not required
• Good morph information
• Info from all major organs
• Real-time sampling of tissues is possible
• Relatively inexpensive

Question 24

What are the disadvantages of an abdominal ultrasound?

Answer 24

• Limited functional information
• Diffuse disease is more difficult to detect
• Sampling is required to classify the disease
• Sedation often required
• Gas interferes with sound transmission

Question 25

How would you prepare the patient?

Answer 25

• Withold food, ideally for 8 hours
• Extensive clipping
• Wash patient down to remove stray hairs
• Apply liberal amounts of coupling gel
• Sedation as required
• Lateral recumbancy