Lecture 10

Question 1

Perpendicular incidence involves (3)

Answer 1

Pulse echo technique
Transmission
Impedance difference

Question 2

Oblique incidence involves (5)

Answer 2

Angle of incidence 
Angle of reflection
Angle of transmission 
Refraction 
Propogation speed differences

Question 3

Both oblique incidence and perpendicular incidence are examples of

Answer 3

Specular incidence

Question 4

Sepecular reflector translates to

Answer 4

Mirror like

Question 5

What boundaries in the body are specular reflectors

Answer 5

Smooth and large

(Diaphragm

Question 6

What happens with the sound to a specular reflectors

Answer 6

Sound will bounce back to the transducer and produce a strong echo

Question 7

What occurs when there is not a smooth large boundary

Answer 7

Scattering occurs

Question 8

What is scattering

Answer 8

Redirection of sound in many directions

Question 9

What is a rougher surface ?

Answer 9

Heterogenous tissue (liver)

Question 10

What does a object have to be to be considered large

Answer 10

Comparable or large than the wavelength

Question 11

Specular reflection has ____ wavelength and ____ object

Answer 11

Small

Large

Question 12

Does scattering help us, why?

Answer 12

Yes

Gives us a good vis of the tissue parenchyma

Question 13

Scattering depends on ____ and _____

Answer 13

Operational frequency and scatterer size (wavelength)

Question 14

Higher operational frequency and less scatterer size (wavelength)

Answer 14

More specular reflection (comes straight back to the transducer )

Increase intesity of echo

The object will be larger than the wavelength

Question 15

What is back scatter

Answer 15

The echo info that comes back to the transducer

Question 16

More frequency more specular refreaction is not true for ______

Answer 16

Rayleigh scattering

Question 17

Rayleigh scattering

Answer 17

Happens when the object is much much smaller than the wavelength

Question 18

We get more information from red blood cells because

Answer 18

They have lots of scattering

Question 19

Scattering intensity is proportional to frequency to the power of

Answer 19

4

Question 20

During speckle, scattering echo sound waves….

Answer 20

Take different paths on the way back to the transducer

Question 21

Speckle Waves coming back can either come back _____ or _____

Answer 21

Constructively or destructively

Question 22

Constructive speckle wave

Answer 22

Reinforce each other

Question 23

Destructive speckle wave

Answer 23

Partially or totally cancel each other

Question 24

Constructive interference is aka

Answer 24

In phase

Question 25

Consructive interferance leads to _____ intensity

Answer 25

Stronger

Question 26

Destructive interferance also known as

Answer 26

Out of phase

Question 27

In order for wave to be constructive, they have to line up ______

Answer 27

Perfectly

Question 28

Some scattered beams coming back in phase and others out of phase can cause

Answer 28

Multiple intensities within one tissue (produces grainy appearance aka speckle)

Question 29

Acoustic speckle is a form of

Answer 29

Acoustic noise

Question 30

Acoustic speckle is the result of

Answer 30

Constructive and deconstrustive interference of staterred sound waves