Key terms 6/7

Question 1

Decibel notation

Answer 1

relative measurement comparision ratio logarithmic

Question 2

Logarithms

Answer 2

a novel method of rating numbers as the logarithm increases by 1 the actual number increases by 10

Question 3

Positive & negative decibels

Answer 3

rep[ort decebels that are increasing or decreasing

Question 4

Decibels & intensities

Answer 4

decibels require 2 intensities, the start level and the actual level at time of measurement, the measured is divided by the start and you get your ratio

Question 5

Attenuation

Answer 5

is the weakening of sound waves as the travel

Question 6

Distance and attenuation

Answer 6

they are directly related, as you travel farther the amount attenuation is greater

Question 7

Frequency and attenuation

Answer 7

directly related, the higher the prequency the higher the attenuation

Question 8

Reflection

Answer 8

a sound waves energy as it strikes a boundry and is redirected back to the source

Question 9

Scattering

Answer 9

random redirection of ultrasound in many directions

Question 10

Absorption

Answer 10

occurs when ultrasonic energy is converted into another form such as heat

Question 11

Specular reflection

Answer 11

the striking of a smooth boundry and the reflection of the beam

Question 12

Diffuse reflection

Answer 12

the striking of a rough boundry and the diffuse reflection of the beam

Question 13

Rayleigh scattering

Answer 13

omni directional scattering of sound waves interaction of ultrasound and RBC’s results in Rayleigh scattering when freq doubles scattering is 16 times greater

Question 14

Attenuation coefficient

Answer 14

number of decibels of attenuation that occurs when sound travels one centimeter units dB/cm

Question 15

Attenuation coefficient in soft tissue

Answer 15

one half the freq

Question 16

Attenuation in media

Answer 16

varies based on density of the media water low air extremely high

Question 17

Half value layer

Answer 17

distance aound travels in a tissue that reduces the intensity to one half its original value

Question 18

Impedance

Answer 18

acoustic resistance to sound traveling in a medium

Question 19

Range equation

Answer 19

the distance calculated by the time the sound takes to travel to the reflector in the body and return to the transducer

Question 20

Time of flight

Answer 20

elapsed time from pulse creatoin to pulse reception also called go return time

Question 21

PRP imaging depth

Answer 21

shallow imaging equals short PRP deeper equals longer PRP

Question 22

PRF imaging depth

Answer 22

shallow imaging equals higher PRF deeper imaging equals lower PRF

Question 23

Reflection and transmission

Answer 23

reflection is the redirection of sound when it strikes a boundry transmission is the sound energy that passes through the boundry and continues on