# Week 5 - Reflection, Transmission, Refraction Flashcards

What happens to sound beam’s energy when it enters tissue?

Some energy is reflected, some energy is transmitted, and some energy is changed.

Most of the ultrasound energy is what?

changed to heat

Describe a specular reflector?

a large, flat, smooth surface; with dimensions larger than the wavelength

What is an example of a specular reflector?

the wall of an artery or vein

What is incidence?

the angle the sound beam hits a specular reflector

an angle of 90 degrees is know as __________

normal incidence

When scanning a specular reflector, what angle gives you the clearest image?

90 degrees

What technique can be used with the probe to obtain a normal incident angle?

heel and toe

What influences how much energy is reflected at a perpendicular incident?

the difference of the tissues at the interface

The ________ the difference in ___________ ___________ , the greater percentage of E that is reflected.

bigger, acoustic impedance

What is an interface?

a boundary or border

What is acoustic impedance?

a characteristic of tissue that affects the strength of an echo

Proportion. Acoustic Impedance and density of tissue.

Directly

Proportion. Acoustic impedance and speed of particle vibration.

Directly

What is the unit of acoustic impedance?

Rayl

What is the reflection coefficient?

% of wave strength that is reflected at an interface

What are the 2 types of reflection coefficient?

Amplitude reflection coefficient and Intensity reflection coefficient

What does ARC stand for?

Amplitude Reflection Coefficient

What is ARC?

the percentage of the strength of the wave that is reflected at an interface

What is the equation for ARC?

ARC% = (Z2 - Z1) / (Z2 + Z1)

The _________ the difference in Z of two adjacent media, the greater the reflected percentage

larger

What is the equation for IRC?

IRC% = [ (Z2 - Z1) / (Z2 + Z1) ] squared

If 60% of the energy is reflected a normal incident, how much is transmitted?

40%