Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
82 Cards in this Set
- Front
- Back
|
attenuation
|
the decrease in intensity , power and amplitude of a sound wave as it travels
|
|
|
True or False:
attenuation is related to speed |
false
|
|
|
what is a unit of attenuation
|
decibels, dB,
|
|
|
What two things affect teh attenuation of sound in soft tissue
|
distance and frequency
|
|
|
The higher the ______ the better the ______ but less _____.
|
1. frequency
2. resolution 3. penetration |
|
|
amplitude and intensity are indicators of the ______ of sound
|
strength
|
|
|
What are three components of attenuation?
|
1. absorption
2. scattering 3. reflection |
|
|
What is the order of attenuation in media
|
air>>bone and lung>>soft tissue>>water
|
|
|
The attenuation of sound in ________is approx. = to the in soft tissue.
|
blood
|
|
|
attenuation is 1. related or 2. unrelated to prop. speed
|
unrelated
|
|
|
a 3MHz sound beam travels thru two media. It attenuates 5 dB in medium A and 6 dB in medium B what is the total attenuation the the soundbeam undergoes....
|
11dB
|
|
|
a 10 MHz soundbeam travels thru two media. It attenuates 5 dB in med. A and 1 dB in Medium B. waht is the total attenuation that the sound beam underoges as it travels thru both media
|
6 dB
|
|
|
a 3MHz sound beam travels 10 cm , 6 cm in med. A and 4 cm in med. B. The total attenuation is 14dB. If the sound beam attenuated 4 dB in med A, then how much attenuation occurred in med. B
|
10 dB
|
|
|
a 3MHz sound beam travels 7 cm in a med. the total attenuation is 5 dB. how much attenuation will a 6 MHzsound beam undergo when traveling 3.5 cm in the same med.
|
5 dB
|
|
|
what is the unit for pressure
|
pascals (Pa), Megapascals (MPa)
|
|
|
intensity (I)
|
rate at which energy passes thru a unit area.
concentration of energy in a sound beam |
|
|
equation for intensity
|
I= Power (watts) over beam area (cm2)
|
|
|
what determines the intensity
|
sound source
|
|
|
can intensity be changed by the sonographer
|
yes
|
|
|
intensity ________ as sound propagated thru the body
|
decreases
|
|
|
is intensity directly or inversly related to power
|
directly
|
|
|
if power is doubled the intensity is ________-
|
doubled
|
|
|
if the power is quartered the intensity is ________
|
quartered
|
|
|
if the amplitude is doubled the intensity increased by a factor of ____
|
four
|
|
|
Intensity is = to
|
power (p) in a wave divided by the area (A).
|
|
|
If beam power increases, intensity _________.
|
increases
|
|
|
If beam area decreases (focusing), intensity ________
|
increases
|
|
|
energy
|
capability to do work
|
|
|
Power
|
rate at which energy is transferred
|
|
|
what are the units of power
|
watts and milliwatts
|
|
|
How is beam area expressed...
|
centimeters squared
|
|
|
if amplitude is doubled; intensity is _________
|
quadrupled
|
|
|
if amplitude is halved intensity is ________
|
quartered
|
|
|
attenuation coefficient
|
is teh attenuation that occurs with each centimeter the sound wave travels
|
|
|
the farther the sound travels the greater or less the attenuation is
|
greater
|
|
|
what are decibels used for :
|
to quantify attenuation
|
|
|
If attenuation coefficient increases, attenuation decreases or increases
|
increases
|
|
|
If path increases, attenuation_________
|
increases
|
|
|
How do you calculate attenuation in decibels
|
1/2 the freq.
|
|
|
As freq. increases, attenuation________
|
increases
|
|
|
how do you calculate the attenuation
|
multiply the attenuation coefficient by the path length
|
|
|
reflections
|
occurs when propagating sound energy strikes a boundary btw two media and some returns to the tx
|
|
|
specular reflection
|
relections from a smooth reflector
|
|
|
When are specular reflectors seen best
|
when sound strikes the reflector at 90 angle
|
|
|
scattering
|
if the boundary btw two media has irregularities then the sound may be chaotically redirected in all directions.
|
|
|
perpendicular incidence
|
denotes a direction of travel of the u\s wave perpendicular to the boundary btw two media
|
|
|
impedance
|
determines how much of an incident sound wave is reflected back thru the first med and how much is transmitted into the second med.
|
|
|
how is impedance measured
|
rayls=z
|
|
|
impedence is a characteristic of
|
medium
|
|
|
what is the equation for impedance
|
impedance=density X speed
|
|
|
name the three components of attenuation
|
absorption, reflection and scattering
|
|
|
Normal incidence
|
perpendicular, orthogonal, right angle, ninety degrees
PORRN |
|
|
Oblique incidence
|
anything other than 90 degress; not at right angles.
|
|
|
incident intensity
|
the intensity of the sound wave at the instant prior to striking a boundry
|
|
|
reflected intensity
|
the portion of the incident intensity that changes direction and returns back from where it came
|
|
|
what is the unit of intensity....
|
w/cm2
|
|
|
what two things describe the stregnth of sound
|
amplitude and intensity
|
|
|
what are the 6 intensities used to describe pulsed sound
|
1. SATA
2. SPTA 3. SAPA 4. SPPA 5. SATP 6. SPTP |
|
|
What happens to imaging depth when frequency increases
|
it decreases
|
|
|
with perpendicular incidence. if two media have the same impedance does reflection take place?
|
no
|
|
|
incidence and reflection angles at a boundry are always ....
|
equal
|
|
|
amplitude is the max. _______ that occurs in an acoustic variable.
|
variation
|
|
|
Bandwidth
|
range of frequencies contained in a pulse
|
|
|
Q factor
|
operating frequency divided by the bandwidth
|
|
|
shorter pulses have ________bandwidths
|
broader
|
|
|
broader bandwidths have higher/lower q factors
|
lower
|
|
|
amplitude is _______ value minus the _________value.
|
maximum
normal |
|
|
(I)ta=(I)pa X DF
|
Temporal average intensity
|
|
|
True or false:
intensity varies across a beam |
true
|
|
|
reflection and transmission coefficients must add up to
|
1 or 100%
|
|
|
if impedences are equal is an echo produced?
|
no
|
|
|
If there is no reflection the media impedences must be _____
|
equal
|
|
|
if there is a large difference btw impedences what type of reflection will you have?
|
nearly total
|
|
|
refraction
|
a change in direction of sound when crossing a boundary
|
|
|
If there is no reflection the media impedences must be _____
|
equal
|
|
|
if there is a large difference btw impedences what type of reflection will you have?
|
nearly total
|
|
|
refraction
|
a change in direction of sound when crossing a boundary
|
|
|
what is the most relevent intensity with respect to tissue heating
|
SPTA
|
|
|
All intensities are reported in what units
|
watts/cm squared
|
|
|
What intensity has the highest value
|
SPTP
|
|
|
what intensity has the lowest value
|
SATA
|
|
|
Duty factor
|
describes teh relationship of beam intensities with time
|
