Week 08 Sound/Ultrasound Lecture

Question 1

How is ultrasound created?

Answer 1

reverse piezoelectric effect

• electricity is applied to a crystal in strong, short pulses which alter its size, producing high frequency sounds

Question 2

How is ultrasound measured?

Answer 2

piezoelectric effect

• sound waves echoing back from the body (interfaces between materials of different acoustic impedance) vibrate a second crystal within the transducer
• vibrations are converted by the crystal into electrical pulses
• pulses are processed and transformed into an image

Question 3

How does an A-mode image from an ultrasound look?

Answer 3

a single transducer scans a line through the body with the echoes plotted on screen as a function of depth