Intensity

Question 0

What is the equation for intensity?

Answer 0

Intensity (w/cm^2) = power/beam area

Question 1

What is intensity?

Answer 1

Intensity is the concentration of the power in a beam. It’s a key parameter for bioeffects.

Question 2

What is peak?

Answer 2

The maximum value

Question 3

What is average?

Answer 3

The mean value

Question 4

What is spatial?

Answer 4

Referring to distance or space

Question 5

What is temporal?

Answer 5

Referring to all time (transmit and receive)

Question 6

What is pulsed?

Answer 6

Referring only to the time the pulse exists (transmit only)

Question 7

What intensity description has the highest value?

Answer 7

SPTP – spatial peak, temporal peak has the highest value.

Question 8

Which intensity description is most important for thermal bioeffects?

Answer 8

SPTA-spatial peak, temporal average is most important with regard to bioeffects.

Question 9

Does an ultrasound beam have the same intensity at different locations within the beam?

Answer 9

No

Question 10

What is a logarithm?

Answer 10

Logarithm is a way of rating numbers by representing the number of tens that are multiplied together to create the number.

Question 11

What is the log of 100? What is the log of 1000?

Answer 11

10x10=100 so the log of 100 = 2
10x10x10=1000 so log of 1000 = 3
Hint: count the zeros

Question 12

What are decibels?

Answer 12

A logarithmic scale, a relative scale-a ratio of the final to the initial strengths.
A comparison, therefore, 2 intensities are needed to calculate decibels.

Question 13

What are the units of relative amplitude?

Answer 13

Decibels

Question 14

What does 3 dB mean?

Answer 14

2 times bigger

Question 15

What does 10 dB mean?

Answer 15

The final intensity is 10 times bigger than the original intensity.

Question 16

What is an intensity ratio of 50 dB?

Answer 16

100,000 times bigger than the original intensity

Question 17

What does 6 dB mean?

Answer 17

Since 3 dB means two times bigger, 6 dB means 2×2. So the final intensity is four times bigger than the original intensity.

Question 18

What does 9 dB mean?

Answer 18

Since 3 dB means two times bigger, 9 dB means 2×2×2. So the final intensity is eight times bigger than the original intensity

Question 19

What does negative decibels mean?

Answer 19

The intensity is decreasing.

Question 20

What does -3 dB mean?

Answer 20

It means the intensity has fallen to half the original value.

Question 21

What does -10 dB mean?

Answer 21

It means we have fallen to 1/10th of the original value.