Module2.2

Question 1

What are the 3 dimensions of the beam extent and beam intensity?

Answer 1

1. Axial direction
2. Beam width, lateral direction
3. Slice thickness or elevation direction

Question 2

How can the ultrasound beam produced be characterised?

Answer 2

In terms of its spatial distribution, determining the dimensions of the beam, the intensity distribution within this region

Question 3

What is theoretical beam profile?

Answer 3

The total extent of the beam including the very low level intensities at the edge of the beam.

Question 4

What is the effective beam profile?

Answer 4

The region where the beam intensity is within 20dB (greater than 1%) of the maximum intensity

Question 5

What are the two zones when the beam profile results from diffraction and interference effects ?

Answer 5

Fresnel zone and fraunhofer zone (near field and far field)

Question 6

What is focussing?

Answer 6

To narrow the ultrasound beam in both lateral direction and elevation/slice thickness direction by using an acoustic lens or curving the face of the individual crystal element(internal focusing)