SPI chapters 1 and 2 Flashcards
absorption
the conversion of sound energy to heat
interface
the dividing line between two different media
parameter
a measurable quanity
oblique incidence
angle of incidence is less than or greater than 90 degrees to the interface
normal incidence
angle of incidence is 90 degrees to the interface
nonspecular reflectors
reflectors that are smaller than the wavelength of the incident beam
medium
any form of matter (liquid,gas,solid)
longitudinal waves
waves in which the molecules of the medium vibrate back and forth in the same direction that the waves are traveling
intensity transmission coefficient
the percentage of sound transmitted at an interface
intensity reflection coefficient
the percentage of sound reflected at an interface
intensity
the power of the wave divided by the area over which it is spread
inertia
newtons principle that states that an object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force
impedance
the resistance to the propagation of sound through a medium
hydrophone
a device used to measure the output intensity of the transducer
hertz
a unit of frequency
half-intensity depth
the depth at which sound has lost half its intensity
frequency
the number of cycles per second
duty factor
the percentage of time that sound is actually being produced
distance
how far apart objects are
density
mass per unit volume
decibels
a unit that establishes a relationship or comparison between two values of power, intensity, or amplitude
damping
the process of reducing the number of cycles of each pulse in order to improve axial resolution
continuous wave
sound that is continuously transmitted
compression
an area in the sound wave of high pressure and density
capacitive micromachined ultrasound transducers
technology used to create comparable transducer technology to piezoelectric materials
beam uniformity ratio
the ratio of the center intensity to the average spatial intensity
backscatter
scattered sound waves that make their way back to the transducer and produce an image on the display
axial resolution
the ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
attenuation coefficient
the rate at which sound is attenuated per unit depth
attenuation
a decrease in the amplitude and intensity of the sound beam as sound travels through tissue
amplitude
the maximum or minimum deviation of an acoustic variable from the average value of that variable
acoustic variable
changes that occur within a medium as a result of sound traveling through that medium
acoustic speckle
the interference pattern caused by scatterers that produces the granular appearance of tissue on a sonographic image
particle motion
the movement of molecules due to propagating sound energy
path length
distance to the reflector
period time
time it takes for one cycle to occur
piezoelectric materials
a material that generates electricity when pressure is applied to it, and one that changes shape when electricity is applied to it
power
the rate at which work is performed or energy is transmitted
pressure
force per unit area or the concentration of force
propagate
to transmit through a medium
propagation speed
the speed at which a sound wave travels through a medium
pulse duration
the time during which the sound is being transmitted; the “on” time
pulse repetition frequency
the number of pulses of sound produced in one second
pulse repetition period
the time taken for a pulse to occur
pulse wave
sound that is sent out in pulses
rarefaction
an area in the sound wave of low pressure and density
rate
the fixed quantity owed as the sound beam travels through tissue
Rayleigh scatterers
small scattering reflectors
reflection
the echo; the portion of sound that returns from an interface
refraction
the change in the direction of the transmitted sound beam that occurs with oblique incidence angles and dissimilar propagation speeds
scattering
the phenomenon that occurs when sound waves are dispersed into different directions because of the small reflector side compared with the incident wavelength
Snell’s law
law used to describe the angle of transmission at an interface based on the angle of incidence and propagation speeds of the two media
sound
a traveling variation in pressure
spatial pulse length
the length of a pulse
specular reflections
reflections that occur when the sound impinges upon a large, smooth reflector at a 90 degree angle
stiffness
the ability of an object to resist compression and relates to the hardness of a medium
total attenuation
the total amount of sound that has been attenuated at a given depth
ultrasound
sound waves of frequencies exceeding the range of human hearing
transverse waves
type of wave in which the molecules in a medium vibrate at 90 degrees to the direction of travel
