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sonography
medical, 2D, cross sectional & 3D anatomical & flow imaging using ultrasound
ultrasound
sound with a frequency greater than what humans can hear (more than 20KHz or 20,000 Hz)
Image
reproduction, representation, or imitation of the physical form of a person or a thing
Linear image
anatomic image presented in a rectangular formaat
transducer
device that converts energy from one form to another
pulse-echo technique
ultrasound imaging when pulses are reflected to produce a display
gray-scale
range of brightness between white and black
scan line
line produced on a display that represents ultrasonic echoes returning from the body
sector image
anatomic image presented in a pie slice shaped format
Doppler effect
change in frequency caused by motion of reflectors
color Doppler display
representation of 2D, real time Doppler-shift information superimposed on a real-time, gray scale, anatomical cross-sectional image
Spectral doppler display
presentation of Doppler info in a quantitative form. Visual display of Doppler spectrum
Pulse echo technique
Ultrasound technique using repeated cycles of ultrasound separated in time by gaps of no ultrasound to create a diagnostic image
wave
traveling variation in one or more quantities called wave variables
acoustic variable
quantiites that vary in a sound wave - pressure, density, particle motion, temperature
vacuum matter
absence of matter
electromagnetic waves
waves that travel at the speed of light and don’t need a medium for propagation
mechanical waves
waves that are categorized by direction of the displacement of individual particles in medium; can be transverse or longitudinal
transverse wave
a wave in which particles in the medium vibrate perpendicular or “transverse” to the direction of the wave motion
longitudinal wave
mechanical compressional wave in which particles in the medium vibrate parallel to the direction of the wave motion
cycle
a completion of one compression and one rarefaction
compression
region of high pressure & density in a sound wave
rarefaction
region of low pressure & density in a sound wave
frequency
number of cycles per second
frequency formula
f = 1 / T (period)
period
time it takes for one cycle to occur
wavelength
length of space over which a cycle occurs
wavelength formula
wavelength = prop. speed / f
stiffness
resistance of a material to compression
propagation speed
speed at which wave moves through a medium
harmonics
frequencies that are even or odd and multiples of fundamental or operating frequency
pulse
a few cycles of ultrasound separated by gaps of no ultrasound
pulse duration
time for one pulse to occur
pulse duration formula
pd = # cycles / frequency
pulse repitition frequency
number of pulses occuring in 1s
PRF formula
PRF = 1 / PRP
pulse repetition period
time from beginning of one pulse to the beginning of the next
duty factor
fraction of time (or %) that pulsed ultrasound is on
duty factor formula
DF % = ( PD / PRP ) x 100
Spatial pulse length
length of space a pulse takes up