Chapter 1 penny Flashcards
the conversion of sound energy to heat
absorption
the interference pattern caused by scatterers that produces the granular appearances of tissue on a sonographic image
acoustic speckle
changes that occur within a medium as a result of sound traveling through that medium
acoustic variables
the maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector
amplitude
a decrease in the amplitude and intensity of the sound beam as sound travels through tissue
attenuation
the rate at which sound is attenuated per unit depth
attenuation coefficient
the ability to accurately identify reflectors that are arranged parallel to the ultrasound beam
axial resolution
scattered sound waves that make their way back to the transducer and produce an image of the display
backscatter
the ratio of the center intensity to the average spatial intensity; also referred to as the SP/SA factor or beam uniformity coefficient
beam uniformity ratio
technology used to create comparable transducer technology to piezoelectric materials
CMUT
an area in the sound wave of high pressure and density
compression
sound that is continuously transmitted
continuous wave
the process of reducing the number of cycles of each pulse in order to improve axial resolution
damping
a unit that establishes a relationship or comparison between two values of power, intensity, or amplitude
decibels
mass per unit volume
density
relationship that implies that if one variable decreases, the other decreases or if one variable increases the other increases
directly related
how far apart objects are; may also be referred to as vibration or displacement
distance
the percentage of time that sound is actually being produced
duty factor
elasticity
stiffness
the number of cycles per second
frequency
the depth at which sound has lost half of its intensity
half-intensity depth
half intensity depth
half value layer thickness
a unit of frequency
hertz
a device used to measure the output intensity of the transducer
hydrophone
the resistance to the propagation of sound through a medium
impedance
Newton’s 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
inertia
the power of the wave divided by the area over which it is spread; the energy per unit area
intensity
the percentage of sound reflected at an interface
intensity reflection coefficient
the percentage of sound transmitted at an interface
intensity transmission coefficient
the dividing line between two different media
interface
relationship that implies that if one variable decreases, the other one increases, and vice versa
inversely related
waves in which the molecules of the medium vibrate back and forth in the same direction that the waves are traveling
longitudinal waves
any form of matter
medium
reflectors that are smaller than the wavelength of the incident beam
nonspecular reflectors
angle of incidence is 90 degrees to the interface
normal incidence
angle of incidence is less than or greater than 90 degrees to the interface
oblique incidence
a measurable quantity
parameter
the movement of molecules due to propagating sound energy
particle motion
distance to the reflector
path length
the time is takes for one cycle to occur
period
a material that generates electricity when pressure is applied to it, and one that changes shape when electricity is applied to it; also referred to as the element or crystal
piezoelectric materials
the rate at which work is performed or energy is transmitted
power
force per unit area of the concentration of force
pressure
to transmit through a medium
propogate
the speed at which a sound wave travels through a medium
propagation speed
the time during which the sound is actually being transmitted; the “on” time
pulse duration
the number of pulses of sound produced in 1 second
pulse repetition frequency
the time taken for one pulse to occur
pulse repetition period
sound that is sent out in pulses
pulsed wave
an area in the sound wave of low pressure and density
rarefaction
the fixed quantity owed as the sound beam travels through tissue
rate
small scattering reflectors
Rayleigh Scatterers
the echo; the portion of sound that returns from an interface
reflection
the change in the direction of the transmitted sound beam that occurs with oblique incidence angles and dissimilar propagation speeds
refraction
the phenomenon that occers when sound waves are dispersed into different directions because of the small reflector size compared with the incident wavelength
scattering
law used to describe the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media
snell’s law
a traveling variation in pressure
sound
the length of a pulse
spatial pulse length
reflections that occur when the sound impinges upon a large, smooth reflector at a 90 degree angle
specular reflections
the ability of an object to resist compression and relates to the hardness of a medium
stiffness
the total amount of sound in dB that has been attenuated at a given depth
total attenuation
type of wave in which the molecules in a medium vibrate at 90 degree to the direction of travel
transverse waves
sound waves of frequences exceeding the range of human hearing
ultrasound
the length of a single cycle of sound
wavelength
infrasound range
less than 20 Hz
audible sound range
20-20,000 Hz
ultrasound range
20,000 Hz or more
diagnostic ultrasound range
between 2 and 15 MHz (or higher)
pressure units
Pascals or pounds per square inch
density units
kg/cm3
particle motion units
feet, inches, centimeters, or miles
period units
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