Ch. 1 & 2 Vocab Flashcards
Sonography
medical two-dimensional, cross-sectional and three-dimensional anatomical and flow imaging using ultrasound.
Ultrasound
sound having a frequency greater than what humans can hear, that is greater than 20kHz (20,000 Hz).
Image
a reproduction, representation, or imitation of the physical form of a person or thing.
Transducer
a device that converts energy from one form to another.
Pulse-Echo Technique
ultrasound imaging in which pulses are reflected and used to produce a display.
Gray-Scale
a range of brightness between white and black.
Scan Line
a line produced on a display that represents ultrasonic echoes returning from the body.
Linear Image
an anatomical image presented in a rectangular format.
Sector Image
an anatomic image presented in a pie slice-shaped format.
Doppler Effect
is a change in frequency caused by motion of reflectors.
Color-Doppler Display
the representation of two-dimensional, real-time Doppler-shift information superimposed on a real-time, gray scale, anatomical, cross-sectional image.
Spectral-Doppler Display
the presentation of Doppler information in a quantitative form. Visual display of Doppler spectrum.
Wave
a traveling variation of one or more quantities.
Sound
a mechanical, longitudinal traveling wave in which particles in the medium move.
Acoustic Variables
sound wave variations of one or more quantities such as pressure, density, temperature or particle motion.
Vacuum Matter
the absence of matter (no matter = no sound)
Electromagnetic Waves
waves that travel at the speed of light and don’t need a medium for propagation (light, microwaves, X-Rays, TV and radio waves.)
Mechanical Waves
waves that are categorized by the direction of the displacement of individual particles in the medium, either 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
a 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
a region of high pressure and density in a sound wave.
Rarefaction
a region of low pressure and density in a sound wave.
Frequency
a number of cycles per second. Hz = 1 cycle/sec Freq(MHz)=PropSpeed(mm/us)/Wavelength(mm) or 1/Period(us)
Period
the time it takes for one cycle to occur (μs). Period(us)=1/Freq(MHz)
Wavelength
the length of space (distance) over which a cycle occurs (mm). Wavelength(mm)=PropSpeed(mm/us)/Freq(MHz)
Stiffness
(hardness) is the resistance of a material to compression.
Propagation Speed
the speed at which a wave moves through a medium (m/s, km/s, mm/μs). Prop Speed (mm/us)=Wavelength(mm)xFreq(MHz)
Harmonics
frequencies that are even and odd multiples of fundamental or operating frequency.
Pulse
a few cycles of ultrasound separated in time by gaps of no ultrasound.
Pulse Duration
the time for one pulse to occur.
PD(us) = Period (us) x # of cycles in pulse
PRF
Pulse Repetition Frequency
the number of pulses occurring in one second. (kHz, Hz)
PRF (kHz) = 1/PRP (ms)
PRP
Pulse Repetition Period
the time from the beginning of one pulse to the beginning of the next one. (ms, μs)
PRP (ms) = 1/PRF (kHz)
DF
Duty Factor
fraction of time that pulsed ultrasound is on. (Unitless or %)
DF(unitless) = PD(us) / PRP (us)
SPL
Spatial Pulse Length
the length of space that a pulse takes up. (mm)
SPL(mm) = wavelength(mm) x # of cycles in pulse
Bandwidth
the range of frequencies contained in a pulse.
Fractional Bandwidth
bandwidth divided by operating frequency.
FB = Bandwidth / Operating Freq.
Operating Frequency
preferred (maximum efficiency) frequency of operation of a transducer. Unit: MHz
Quality Factor
the reciprocal of fractional bandwidth (operating frequency divided by bandwidth). Unitless
QF = Operating Freq / Bandwidth
Amplitude
the maximum variation that occurs in an acoustic variable (pressure, density, temperature, particle motion). Units: Pa, g/cm3, cm, dB, etc.)
Intensity
the rate at which energy passes through a unit area. Unit: W/cm2, mW/cm2
Intensity (W/cm2) = Power (Watts) / Area (cm2)
Power
the rate of doing work. Unit: Watts
Energy
the capability to do work. Unit: Joule (J)
Attenuation
the weakening of sound as it propagates. Unit: dB
Attenuation Coefficient
the rate at which the sound decreases in amplitude and intensity as it moves through a medium. Unit: dB/cm
Atten Coeff = 0.5dB/cm x Freq (MHz)
Reflection
echo or a portion of sound returned from a media boundary. OR is the sound moving in the opposite direction after encountering a boundary between 2 media.
Absorption
conversion of sound to heat.
Scattering
diffusion or redirection of sound in several directions upon encountering tissue interfaces and heterogeneous tissues.
Scatterer
an echo-generated structure.
Echoes
reflected & scattered sound waves.
Incident Sound
the initial sound prior to hitting a boundary between 2 media.
Reflected Sound
the sound moving in the opposite direction of the incident sound after encountering a boundary between 2 media.
Transmitted Sound
the sound that continues to the next boundary after encountering a boundary between 2 media.
Incident Intensity
the strength of the initial beam prior to hitting a boundary between 2 media.
Reflected Intensity
the strength of the beam moving in the opposite direction of the incident sound (or beam) after encountering a boundary between 2 media.
Transmitted Intensity
the strength of the beam that continues to the next boundary after encountering a boundary between 2 media.
Impedance
the acoustic resistance to sound traveling in a medium. Unit: rayls
Impedance (rayls) = density (kg/m3) x Prop Speed (m/s)
Perpendicular Incidence
sound direction that is perpendicular to the boundary between media.
Incident Reflection Coefficient
IRC
the fraction of incident intensity that is reflected. Unitless, %
IRC = Reflected Intensity (mW/cm2) / Incident Intensity (mW/cm2)
Intensity Transmission Coefficient
ITC
the fraction of incident intensity transmitted into the second medium. Unitless, %
ITC= 1- IRC or ITC= Transmitted Intensity (mW/cm2) / Incident Intensity (mW/cm2)
Incident Angle
the angle between incident sound direction and a line perpendicular to the media boundary.
Reflected Angle
the angle between the reflected sound direction and a line perpendicular to the media boundary.
Transmission Angle
the angle between the transmitted sound direction and a line perpendicular to the media boundary.
Oblique Incidence
the direction of travel of the incident sound wave that is NOT perpendicular to the boundary between the media.
Refraction
a change in the direction of sound when it crosses a boundary (from Latin term “to turn aside.”)
Specular Reflectors
reflectors which occur when thebeamis small compared to the boundary (wavelength is small to the boundary.)
Nonspecular Reflectors
reflectors which occur when thebeamis large compared to the boundary (wavelength is large to the boundary.)
Backscatter
sound scattered back in the direction from which it originally came.
Speckle
a form of acoustic noise in sonographic imaging.
Interference
produced when several echoes are generated simultaneously within the pulse as it interacts with the scatterers.
Constructive Interference
occurs when the echoes arrive at the transducer in such a way that they reinforce each other.
Destructive Interference
occurs when the echoes arrive at the transducer in such a way that they partially or totally cancel each other.
Contrast Agents
a liquid suspension intravenously injected into the circulatory system to increase echogenicity.
13μs/cm Rule
13 microseconds of round-trip travel time are required for each cm of distance from the transducer to the reflector.
