Final Physics review

Question 1

When wave intensity doubles what is the change in decibel

Answer 1

3db incfrdase

Question 2

Wehn intensity increases 10 fold what is change in db

Answer 2

10

Question 3

What 3 processes contribute to wave attenuation?

Answer 3

Reflection, scattering absorption

Question 4

What ar e2 forms of reflection?

Answer 4

Specular - mirror reflections that don’t return to transducer. Diffuse reflection - backscatter

Question 5

Diffuse reflection vs scattering

Answer 5

scattering reflects in many directions. Diffuse reflection is bounced back at different angles.

Question 6

What are typical units of attenuation?

Answer 6

It summarizes reflection, scattering and absorption ad 2Db/cm

Question 7

What is attenuation coefficient in soft tissue

Answer 7

1/2 dB/cm/MHz

Question 8

Order of attenuation of different medium

Answer 8

water, blood/urine, fat, soft, muscle, bone/lung, air

Question 9

What is half value layer thickness

Answer 9

Term referring to attenuation. Distance to reduce attenuation by half.

Question 10

What is acoustic impedance definition

Answer 10

Density of medium x speed of sound in medium

Question 11

Unit of acoustic impedance

Answer 11

Rayls

Question 12

What does acoustic impedance relate to?

Answer 12

Relates to the amount of reflection at a tissue boundary layer

Question 13

How does the attenuation coefficient relate to the ultrasound frequency in soft tissue?

Answer 13

In soft tissue attenuation coefficient (in dB/CM) is 1/2 the frequency

Question 14

Definition of incident intensity

Answer 14

Sound wave’s intensity before striking boundry

Question 15

What is the intensity reflection and transmission coefficients and what are units?

Answer 15

Percentages reflecting how much is reflected vs transmitted

Question 16

At soft tissue boundary how much is reflected vs transmitted

Answer 16

99% transmitted

Question 17

When a sound wave hits a tissue boundary at 90 degree angle what determines whether reflection occurs?

Answer 17

Only the impedance difference between the two

Question 18

What is equation intensity transmission coefficient with normal incidence?

Answer 18

ITC (%) - transmitted intensity/incident intensity x 100

Question 19

Is it easy to determine how much transmission occurs with oblique incidence?

Answer 19

No - there is no predictable way to make determination

Question 20

If US signal hits interface at oblique angle, what happens?

Answer 20

Part reflected at incident angle, the other bit transmitted and refracted based on the speed of sound difference between the two media

Question 21

If you know attenuation coefficient what is ultrasound frequency?

Answer 21

F = attenuation coefficiente x 2

Question 22

What is range equation

Answer 22

1.54 mm/us x (go return time (us))/2

Question 23

What is the 13 us rule?

Answer 23

For every 13us that sound travels in soft it is 1 cm deeper into body

Question 24

What is PRP (us) in soft tissue

Answer 24

imaging depth (cm) x 13 us/cm

Question 25

Another name of PRP

Answer 25

Go return time

Question 26

How thick is matching layer vs crystal

Answer 26

1/4 vs 1/2 wavelength

Question 27

What is quality factor equation

Answer 27

Main frequency/bandwidth

Question 28

What has a deeper focus high or low frequency? Wide or narrow?

Answer 28

Wide and high frequency has deeper focus

Question 29

Equation for focal depth

Answer 29

Diameter^2 x Frequency/6 in mm