chapter 1-3 Flashcards
frequency
cycles per second hertz
amplitude
Measures from middle or undisturbed, value to the maximum value
wavelength
distance or length of one complete cycle
human hearing
20hz-20kHz
high frequency
more cycles per second- better resolution but less penetration
lower frequency
less cycles per second- less resolution but more penetration
Pulse waves
pulse allow the ultrasound crystals to “talk” during the generation of sound and to “listen” between pulses
Unrelated
Two items that are not associated
related
two items that are associated or affiliated. Does not have to be specific
Directly related or directly proportional
two items that are associated such that when one item increases, the other increases. lower left to upper right
inversely related or inversely proportional
one item increases, the other decreases. upper left to lower right
reciprocal relationship
two numbers with a reciprocal relationship are multiplied together the result is 1. when one increases the other decreases
units of length
distance, circumference: cm, feet
units of area
cm2, ft2
units of volume
cm3, ft3
positive exponents has a value
greater than 10
negative exponents has a value
less than 1
exponents of zero has a value
Between 1 and 10
if we speak of frequency
talking about MEGAhertz
if we speak about period
talking about MICROseconds
tissue is also known as
media-medium
sound is a
mechanical wave
compressed
squeezed together
rarefield
stretched apart
sound travels in
a straight line
sound waves are
Longitudinal waves
Acoustic propagation propereties
effects of the medium upon the sound wave
biologic effects
effects of thee sound wave upon the biologic tissue through which it passes
what are the three acoustic variables
pressure, density, distance
Pressure
concentration of force in an area
what are the units of pressure
Pascals (Pa)
Density
concentration of mass in a volume
what are the units of density
kg/cm3
Distance
measure of particle motion
what are the units of distance
cm, feet, miles
sound waves are also known as
acoustic waves
Transverse waves
perpendicular to the direction that the wave propagates
longitudinal waves
particles move in the same direction that the wave propagates.
sound is what kind of wave?
Longitudinal wave
in-phase waves
when their peaks occur at the same time and at the same location. “in-step”
out-of-phase
their peaks occur at different times, so do their troughs. “out-of-step”
interference
waves lose their individual characteristics at that moment and combine to form a single wave
constructive interference
wave is larger than either of its comonents
destructive interference
resultant wave is smaller than one of its comonents
both constructive and destructive interference occur when
frequencies of the wave differ
parameters
describe features of a sound wave
source
a sound wave is the ultrasound system and transducer
Period
is the time it takes a wave to vibrate a single cycle
units of Period
time, microseconds,seconds, hours, days
Typical value of Period
0.06-0.5 Microseconds
6x10^-8 to 5x10^-7
0.06 to 0.5 micros
0.00000006 to 0.0000005 seconds
Period is Determined by
sound source
can a Sonographer adjust Period?
NO
Frequency
the number of particular events that occur in a specific duration of time. the number of cycles that occurs in one second
what are the units of frequency
per second, 1/second=1 hertz
1,000 cycles/second=1 kHz
1,000,000 cycles/second=1 MHz
Typical value of Frequency
2 MHz-15MHz
2 million-15 million per second
Frequency is determined by
sound source
is Frequency adjustable?
NO
Frequency of infrasound
less than 20 Hz
Frequency of Audible sound
between 20 Hz and 20 KHz
Frequency of Ultrasound
Greater than 20 KHz (20,000Hz)
Frequency is important to ultrasound because
it affects penetration and image quality
Period and frequency are
inversely related to each other
period and frequency have a specific relationship called
reciprocal
Hertz means
events per seond
What are the three Bigness parameters
Amplitude, Power, Intensity
Amplitude
Bigness of a wave.
Difference between the maximum value and the average or undisturbed value of an acoustic variable. Difference between the minimum value and the average value of the acoustic variable
Units of Amplitude
Pressure- Pascals
Density- g/cm3
Particle motion- cm, inches-any distance
Decibels (dB)
typical values of Amplitude
1 million pascals (1 MPa) - 3 million pascals ( 3 MPa)
Amplitude is determined by
sound source
Can amplitude be adjustable?
Yes, allows the Sonographer to alter initial amplitude of a wave
Power
rate of energy transfer or the rate at which work is performed
Units of Power?
Watts
What is the typical values of Power?
0.004-0.090 watts
(4 - 90 milliwatts)
Amplitude and power are related how?
describe the size or magnitude of a wave.
squared
number is multiplied by itself
Power is determined by?
Sound source
is Power adjustable?
Yes, Allows Sonographer to alter the initial power of a wave
Intensity
concentration of energy in a sound beam
what are the units of intensity?
Watts/square centimeter, W/cm2
watts form power and cm2 from beam area
what are the typical values of intensity?
0.01-300 W/cm2
how is intensity determined by?
sound source
Is intensity adjustable?
Yes, alters the initial intensity of a wave
intensity formula
intensity (w/cm2)=power(w) / area(cm2)
Amplitude, power, and intensity describe what?
magnitude or strength of a wave. Directly Related
is intensity proportional to power?
YES
relationship between intensity and amplitude?
intensity is proportional to the wave’s amplitude squared
Wavelength
distance or length of one complete cycle
units of a wavelength
mm, meters, or any other unit of length
typical value of wavelength
0.1-0.8 mm
Wavelength is determined by
BOTH the Source and the Medium
can you adjust wavelength?
NO
in soft tissue, sound with a frequency of 1 MHz has a wavelength of
1.54 mm
sound with a frequency of 2 MHz has wavelength of
0.77 mm in soft tissue
Wavelength formula
wavelength (mm) =1.54 mm/milliseconds/ frequency (MHz)
Shorter wavelengths are created by
high frequency sound
higher quality images have
greater detail
Propagation speed
rate at which a sound wave travels through a medium
what are the units of Propagation speed
meters per second, mm/ms, or any distance divided by time
what are the typical values of propagation speed?
500 m/s-4000 m/s depending on the tissue
propagation speed is determined by
medium through which the sound is traveling
is propagation speed adjustable?
NO
Biologic medium is called
soft tissue
the speed of sound in soft tissue is
1,540 m/s
1.54 mm/ms
1.54km/s
1 mile per second
sound travels fastest in
solids
sound travels slower in
liquid
sound travels slowest in
gases
Speed formula
speed (m/s) = frequency (Hz) x wavelength (m)
Two characters of Medium affect speed of sound
stiffness, density
Stiffness
ability of an object to resist compression
how does stiffness affect speed?
stiffness and speed are directly related
Bulk modulus
stiffness
Elasticity and compressibility are
the opposite of stiff
how does density affect speed?
Density and speed are inversely related
Stiffness has the greatest influence on
speed
sound travels slowly through
air
slowest to fastest propagation speeds
air
lung
fat
soft tissue/blood
tendon
bone
Pulse duration
Actual time from the start of aa pulse to the end of that pulse. Single transmitted, talking or on time
Units for pulse duration
Time: Microseconds
typical values of pulse duration
0.3-2.0 microseonds
pulse duration is determined by
sound source
is pulse duration adjustable?
NO
