Ultrasound

Question 1

Ultrasound frequencies are greater than…

Answer 1

20kHz

Question 2

For medical imaging ultrasound frequencies are usually within…

Answer 2

1MHz to 20MHz

Question 3

List 3 benefits of using ultrasound imaging instead of X-rays.

Answer 3

1. Can detect and distinguish many different types of tissues in the body.
2. Much safer because ultrasonic waves are not ionsing.
3. Results can be shown in real time.

Question 4

Explain how transducers generate ultrasonic waves and receive data from reflections.

Answer 4

Piezoelectric crystals vibrate when a small voltage is turned on and off on either side of the crystal, creating an ultrasonic wave. When waves are reflected back the crystals vibrate and cause a small voltage to be generated which sends data to an imaging computer.

Question 5

Describe an A-scan.

Answer 5

• No image is produced
• Shows reflected intensities over time
• Measurements can be taken to nearest mm.

Question 6

Describe a B-scan

Answer 6

• Uses an array of transducers
• Many echoes collected and collated
• Images produced

Question 7

Define acoustic impedance.

Answer 7

The resistance to sound travelling through a substance.