Ultrasound

Question 1

How does an ultrasound transducer work?

Answer 1

A high frequency pd is sent to the electrodes
This cause the crystal to deform at the same frequency and produce ultrasound waves at this frequency
These waves then hit what is being analysed and are reflected back at a new frequency
This deforms the crystal so a new pd is detected along the electrodes

Question 2

What is the piezoelectric effect?

Answer 2

when a crystal is put under stress it produces a pd. The reverse of this effect means when a crystal has a pd applied then a crystal will deform

Question 3

What is the purpose of the plastic nose on an ultrasound transducer?

Answer 3

Has the correct acoustic impedance to ensure maximum transmission and focus the ultrasound beam

Question 4

What is an ultrasound A Scan?

Answer 4

Use only one detector where a pulse is sent and a series of reflections are received.
The time between reflections corresponds to the distance.
They are typically used to detect detached retinas

Question 5

What is an ultrasound B Scan?

Answer 5

B scans use multiple emitters (512 usually) to produce a line that is 512 dots long. As the probe is rotated it means a full 2D image is formed.
This is what is usually used for baby scans

Question 6

What is acoustic impedance?

Answer 6

A measure of how difficult it is for an acoustic wave to travel through a medium

Question 7

What is the equation for acoustic impedance?

Answer 7

Z= pxc = density x speed of sound in the medium

Question 8

what is the equation for doppler shift in ultrasound?

Answer 8

Δ λ/λ= 2vcos(@)/c

Question 9

What is the equation for the intensity of the reflected wave?

Answer 9

Ir/Ii = (Z2 - Z1)^2/(Z2+Z1)^2