Ultrasound

Question 1

What is the wave equation?

Answer 1

Speed of sound c = root( K / p)
K is bulk modulus
p is density

Question 2

What is the speed of sound in soft tissue?

Answer 2

1540 m/s

Question 3

Equation for the length of the near field

Answer 3

L = a^2 / h
a is radius
h is wavelength

Question 4

Equation for far field divergence

Answer 4

Angle = arcsin ( 0.61h / a)
h is wavelength
a is radius

Question 5

Wavelength to frequency equation

Answer 5

c = hf
h is wavelength
f is frequency

Question 6

Width at focus equation

Answer 6

W = F h / a
F is focal length
h is wavelength
a is radius

Question 7

What does beam width at focus relate to?

Answer 7

Spatial resolution

Question 8

Medical ultrasound range?

Answer 8

1.5 - 15 MHz

Question 9

Name the 3 transducer types

Answer 9

Linear array
Curved array
Phased array

Question 10

Name the 4 ultrasound modes

Answer 10

B-mode
M-mode
Colour Doppler
Pulsed wave Doppler

Question 11

Equation for relative intensity level

Answer 11

RIL = 10 log (I2/I1) dB

Question 12

Equation for relative pressure level

Answer 12

RPL = 20 log (p2/p1) dB

Question 13

Equation for acoustic impedance

Answer 13

Z = p/u
p is acoustic pressure
u is particle velocity

Z = root ( Kp) = pc
K is bulk modulus
p is density
c is speed of sound

Question 14

Equation for acoustic intensity

Answer 14

I = pu = p^2 / Z
p is acoustic pressure
u is particle velocity
Z is acoustic impedance

Question 15

Explain reflection at a boundary

Answer 15

There must be continuity of pressure so the reflected wave is 180 degrees out of phase