Ultrasound

Question 1

What is ultrasound?

Answer 1

Sound above 20,000Hz which is higher than the human hearing range.

Question 2

What are the parts of a longitudinal wave?

Answer 2

• Compressions (squashed) and rarefactions (spaced out), pressure waves
• Can’t travel through vacuums, the denser the medium the faster the wave travels
• Vibrations are parallel to the direction of the wave

Question 3

How does ultrasound break down kidney stones?

Answer 3

• High-powered ultrasound beam is fired at the kidney stones
• Ultrasound energy causes the stones to vibrate and break apart into smaller pieces
• They are then excreted out normally

Question 4

How is ultrasound used for a body scan?

Answer 4

• Pulse of ultrasound is sent into the body
• At each boundary between different tissue some ultrasound is reflected and the rest is transmitted
• The returning echoes are recorded and used to build up an image of the internal structure

Question 5

Why can ultrasound be used for body scans?

Answer 5

• When ultrasound is reflected from different interfaces in the body the depth of each structure is calculated by knowing the speed of ultrasound and the time taken for the echoes to return by distance = speed X time
• The proportion of ultrasound reflected depends on the density of the material and therefore the speed of sound in these materials
• If the tissues are very different in density most of the ultrasound will be reflected leaving little to penetrate further into the body

Question 6

Why is ultrasound preferred to x-rays?

Answer 6

• Able to produce images of soft tissue

- Doesn’t damage living cells