Physics Principles Flashcards
process whereby sound energy is dissipated in a medium, primarily in the form of heat
absorption
having to do with sound
acoustic
resistance of sound as is propagates through a medium
acoustic impedance
effects on sound beam caused by the medium; includes pressure, density, and particle motion (distance and temperature)
acoustic variables
realting to the strength of the compression wave; max variation of an acoustic variable
amplitude
attenuation occurring with each centimeter that sound travels
attenuation coefficient
range of frequencies found in pulse ultrasound
bandwidth
distance around the perimeter of an object
circumference
region of high pressure or density in a compression wave
compression
a nonplused wave in which cycles repeat indefinitely
continuous wave
one complete variation in pressure or other acoustic variable
cycle
a unit used to compare the ratio of intensities or amplitudes of two sound waves or two points along the wave
decibel
concentration of mass, weight, or matter per unit volume
density
dependence of velocity of other physical parameters on frequency
dispersion
amount of space from one object to another
distance
fraction of time that pulse ultrasound is on
duty factor
capability of doing work
energy
comparison of range of frequencies (bandwidth) with operating frequency
fractional bandwidth
number of cycles in a wave occurring in 1 second
frequency
original operating frequency
fundamental frequency
thickness of tissue required to reduce the intensity of the sound beam by one-half; also known as depth of penetration, half boundary layer, or penetration depth
half value layer (HVL)
echoes of twice the frequency transmitted into the body that reflect back to the transducer, which improves image quality
harmonic frequency
once cycle per second; unit of frequency
hertz (Hz)
determines how much of an incident sound wave is reflected back from the first medium and how much is transmitted into the sound beam
impedance
direction of incident beam with respect to the media boundary
incident angle
initial or staring beam
incident beam
rate at which energy transmits over a specific area
intensity
one thousand cycles per second
kilohertz (kHz)
wave traveling in straight line
longitudinal wave
incident ultrasound traveling at an oblique angle to the media boundary
oblique incidence
time to complete one cycle
period
incident ultrasound traveling at an angle perpendicular to the media boundary
perpendicular incidence
concentration of force
pressure
speed at which a wave moves through a medium
propagation speed
a collection of a number of cycles that travel together
pulse
portion of time from the beginning to the end of a pulse
pulse duration
number of pulses per second
pulse repetition frequency
time between the beginning of one cycle and the beginning of the next cycle
pulse repetition period
a few pulses of ultrasound followed by a longer pause of no ultrasound.
pulse ultrasound
for short pulses, the Q factor is equal to the number of cycles in a pulse; the lower the Q factor the better the image
Quality Factor (Q factor)
regions of low pressure or density in a compression wave
rarefaction
occurs when the reflector is much smaller than the wavelength of the sound beam
Rayleigh’s Scatter
the beam redirected back to the transducer after striking a media boundary
reflected beam
redirection (return) of a portion of the sound beam back to the transducer
reflection
angle between the reflected sound and a line perpendicular to the media boundary
reflection angle
change in direction of the sound wave after passing from one medium to another
refraction
redirection of sound in several directions on encountering a rough surface; also known as nonspecular reflections
scattering
a traveling variation of acoustic variables
sound
relating to space
spatial
multiple echoes received at the same time generating interference in the sound wave, resulting in a grainy appearance of the sonogram
speckle
distance over which a pulse occurs
spatial pulse length
these comprise the boundaries of organs and reflect sound in only one direction; angular dependent
specular reflections
these comprise the boundaries of organs and reflect sound in only one direction; angular dependent
specular reflections
resistance of a material to compression
stiffness
relating to time
temporal
the sound beam continuing on to the next media boundary
transmitted beam
amount of occupied space of an object in three dimensions
volume
distance (length) of one complete cycle
wavelength
below 20Hz; below human hearing
infrasound
Above 20Hz and below 20,000Hz; within human hearing
audible sound
Above 20,000Hz (20kHz); above human hearing
ultrasound
Sound waves carry _____ not matter, from one place to another.
energy
Give the values and symbol for the following metric prefixes: Tetra Giga Mega Kilo Hecto Deca deci centi milli micro nano pico
Tetra = trillion 10^12 = T Giga = billion 10^9 = G Mega = million 10^6 = M Kilo = thousand 10^3 = k Hecto = hundred 10^2 = h Deca = ten 10^1 = Da deci = tenth 10^-1 = d centi = hundredth 10^-2 = c milli = thousandth 10^-3 = m micro = millionth 10^-6 = u (the special looking u) nano = billionth 10^-9 = n pico = trillionth 10^-12 = p
Whats the propagation speed in soft tissue?
1.54mm/us or 1540 m/s
in soft tissue what is the attenuation coefficient equal too?
half the transducer frequency
attenuation happens as a result of?
absorption
reflection
scattering
what are the units of the following: attenuation attenuation coefficient density half value layer impedance
attenuation = dB attenuation coefficient = dB/cm density = kg/m^3 half value layer = cm impedance = rayls
