Ultrasound

Question 1

How does an ultrasound work?

Answer 1

1. High-frequency sound waves are transmitted from a transducer.
2. These sound waves are then reflected by different tissue types in different ways.
3. The reflected sound waves are then picked up by the ultrasound transducer.
4. The sound waves are then transformed into an image by special software.

Question 2

How do bones, fat and stones appear?

Answer 2

Hyperechoic signal –> bright as most ultrasound waves are reflected

Question 3

How does fluid and fluid-filled structures appear?

Answer 3

Anechoic signal –> appears black as there is no reflection of ultrasound waves.

Question 4

How does cartilage and bone appear?

Answer 4

A hypoechoic signal –> appears dark as most waves pass through the tissue.

Question 5

Getting started: what are the first 3 steps of performing an US?

Answer 5

1. Turning on the machine (easy, but often overlooked; often a button in the upper left or right corner of the keypad)
2. Entering the patient’s information (e.g. name, date of birth, hospital number)
3. Selecting an appropriate ultrasound probe for the area being examined.

Question 6

What 4 machine variables should be considered in order to optimise an image?

Answer 6

1. Frequency (adjust according to what structures looking at)
2. Depth (capture the structures you want to see, so as large as possible)
3. Gain
4. Focal points

Question 7

What does ‘gain’ refer to? How is it controlled?

Answer 7

• Brightness control – ‘amplifier of returning signal’
  
  • Adjusting the gain of an ultrasound changes the brightness of the image
    
    • Typically controlled by a knob
• Set to show optimal contrast between tissues
• The gain should be adjusted until fluid appears black and soft tissue appears mid-grey with some parts of the image appearing white

Question 8

How should the ‘depth’ be controlled?

Answer 8

Deeper structure = greater the depth on the screen (button on side allows you to adjust this)

• Depth measures are shown in cm on the side of the ultrasound monitor
• It is often best to begin deep to orientate yourself and then work more superficially to bring the object of interest into the middle of the screen.

Question 9

Typically, what are the 3 different types of ultrasound probe?

Answer 9

1. Linear probe
   2.

Question 10

For a linear probe, describe its:

a) frequency
b) resolution and depth
c) useful for?

Answer 10

a) High frequency (7-15MHz):
b) High resolution but superficial (1-6cm) depth
c) Good for vascular access, nerve blocks, assessment of testes and superficial lung tissue

Question 11

For a curvilinear probe, describe the;

a) frequency
b) resolution and depth
c) used for?

Answer 11

a) Low frequency (2-5MHz)
b) Low resolution, but greater depth (10-20cm)
c) Useful for abdominal, pelvic, obstetric and deep lung tissue

Question 12

For a phased probe, describe the:

a) frequency
b) used for?

Answer 12

a) Lowest frequency (1-3MHz)
b) Useful for echocardiography

Question 13

How should an ultrasound probe be held?

Answer 13

• Typically, there is a dot or a cross on the probe, this correlates with a dot on the left side of the screen.
• This marker should be toward the patient’s right in transverse and head in longitudinal.

Question 14

Once you’ve chosen an appropriate probe and are holding it right, what are the next 3 steps of performing an ultrasound?

Answer 14

1. Applying gel to the probe and patient.
2. Placing the probe onto the patient and observing the images on the screen.
3. Adjusting the settings to achieve an optimal view.

Question 15

General tips for achieving an optimal view?

Answer 15

• Use lots of gel
• Make good contact between the probe and skin (whilst ensuring the patient is comfortable)
• Dim the lights to improve your view of the monitor
• Ensure the probe is perpendicular to the skin