Ch. 1 - Foundations of Sonography Flashcards
Change in the direction of propogation of a sound wave transmitted across an interface where the speed of sound varies
refraction
Angle at which a sound beam strikes the interface between two types of tissue
angle of incidence
Power per unit area
intensity
Special material in the transducer that has the ability to convert electric impulses into sound waves
crystal
Propagation of energy that moves back and forth or vibrates at a steady rate
wave
Any device that converts energy from one form to another
transducer
Number of cycles per second that a periodic event or function undergoes
frequency
Measure of a material’s resistance to the propagation of sound; expressed as the product of acoustic velocity of the medium and density of the medium
acoustic impedance
Generation of electric signals as the result of an incident sound beam on a material that has piezoelectric properties
piezoelectric effect
Region over which the effective width of the sound beam is within some measure of its width at the focal distance
focal zone
Reduction in amplitude and intensity of a sound wave as it propagates through a medium
attenuation
Passive force in opposition to another, active force; occurs when tissue exerts pressure against the flow
resistance
Surface forming the boundary between media having different properties
interface
Region of increased particle density
compression
Distance over which a wave repeats itself during one period of oscillation
wavelength
Refers to the minimum distance between two structures positioned along the axis of the beam where both structures can be visualized as separate objects
axial resolution
Rate of energy flow over the entire beam of sound
power
Unit used to quantitatively express the ratio of two amplitudes or intensities
decibel (dB)
1,000,000 Hz
megahertz (MHz)
Ability of the transducer to distinguish between two structures adjacent to one another
resolution
Time interval required for generating the transmitted pulse
pulse duration
Sequence of events occurring at regular intervals
cycle
Speed of the ultrasound wave; determined by tissue density
velocity
Minimum distance between two objects at which they still can be displayed as separate objects
lateral resolution
Unit for frequency; equal to 1 cycle per second
hertz (Hz)
Field closest to the transducer during formation of the sound beam
Fresnel zone
Angle of incidence at which the sound beam strikes the interface
angle of reflection
1000 Hz
kilohertz (kHz)
Field farthest from the transducer during formation of the sound beam
Fraunhofer zone
Thickness of the section in a patient that contributes to echo signals on any one image
slice thickness
Sound transmitted and received intermittently with one transducer
pulsed wave (PW) Doppler
Ability to compensate for attenuation of the transmittal beam as the sound wave travels through tissue in the body
time gain compensation (TGC)
Change in frequency of a reflected wave; caused by motion between the reflector and the transducer’s beam
Doppler shift
One transducer continuously transmits sound, and one continuously receives sound; used in high-velocity flow patterns
continuous wave (CW) Doppler
Normal pattern of vessel flow; flow in the center of the vessel is faster than it is at the edges
laminar
Rate at which images are updated on the display; dependent on transducer frequency and depth selection
frame rate
Analysis of the entire frequency spectrum
spectral analysis
Technical artifact that occurs when the frequency change is so great that it exceeds the sampling view and pulse repetition frequency
aliasing
In pulse-echo instruments, it is the number of pulses launched per second by the transducer
pulse repetition frequency (PRF)
Ability of the system to accurately depict motion
temporal resolution
Ratio of the largest to the smallest signals that an instrument or a component of an instrument can respond to without distortion
dynamic range
In pulsed Doppler, the Doppler signal must be sampled at least twice for each cycle in the wave if Doppler frequencies are to be detected accurately
Nyquist sampling limit
Strength of the ultrasound wave measured in decibels
amplitude
Measure of strength of the ultrasound signal
gain
Echo fill-in of the spectral window that is proportional to the severity of stenosis
spectral broadening
Ultrasound instrumentation that allows the image to be displayed many times per second to achieve a “real-time” image of anatomic structures and their motion patterns
real time
B-mode scanning technique that permits the brightness of the B-mode dots to be displayed in various shades of gray to represent different echo amplitudes
gray scale
Amount of change in the returning frequency compared with the trasmitting frequency when the sound wave hits a moving target such as blood in an artery
frequency shift
Sample site from which the signal is obtained with pulsed Doppler
gate
Angle that the reflector path makes with the ultrasound beam; the most accurate velocity is recorded when the beam is parallel to flow
Doppler angle
Acoustics is the study of _______________, _______________, and _______________ sound waves.
generating, propagating, receiving
Ultrasound is defined as sound frequencies beyond the upper limits of human hearing, that is, greater than _______________.
20 kHz
Name three pioneers who made a significant contribution to ultrasound.
Douglass Howry, Hertz and Elder, John Wild
The terms _______________, _______________, and _______________ have all been used to describe an imaging technique by which soft tissue structures of the body are visualized by recording the returning reflection of ultrasonic waves directed into the body.
diagnostic medical ultrasound, ultrasound, ultrasonography
The term that applies to the ultrasound evaluation of cardiac structures is _______________.
echocardiography
One who performs ultrasound studies and gathers diagnostic data under the direct or indirect supervision of a physician is a _______________.
sonographer
List the qualities of a good sonographer.
Intellectual curiosity, perseverance, ability to conceptualize 2D images into a 3D format, quick/analytical mind, technical aptitude, good physical health, independence/initiative, emotional stability, communication skills, dedication
As the ceramic element vibrates, it periodically presses against and pulls away from the adjacent medium with resultant particle _______________ and _______________ in the medium.
compression, rarefaction
A transducer converts _______________ energy into _______________ energy
electrical, mechanical
A propagation of energy that moves back and forth or vibrates at a steady rate is a _______________.
wave
The time required to produce each cycle depends on the _______________ of the transducer.
frequency
The distance between two peaks over a period of time is the _______________.
wavelength
Wavelength is inversely related to frequency, which means that the higher the frequency, the _______________ the wavelength.
shorter
As frequencies become higher, the pulse duration _______________, yielding a decrease in the depth of field.
decreases
The rate at which energy is transmitted is referred to as the _______________.
power
Power per unit area is defined as _______________.
intensity
If you double the power, the intensity _______________.
doubles
The piezoelectric effect was first described by the _______________ brothers in 1880.
Curie
Air-filled structures, such as as lungs and stomach, or gas-filled structures, such as bowel, _______________ sound transmission.
impede
Bone conducts sound at a _______________ speed than soft tissue.
faster
Normal transmission of sound through soft tissue travels at _______________ m/sec.
1540
Acoustic impedance is the product of the _______________ in a medium and the density of that medium.
velocity of sound
The angle of reflection is equal to the _______________.
angle of incidence
If specular reflectors are aligned _______________ to the direction of the transmitted pulse, they reflect sound directly back to the active crystal elements in the transducer and produce a strong signal.
perpendicular
The sum of acoustic energy losses resulting from absorption, scattering and reflection is the _______________.
attenuation
Minimum reflector separation along the sound path required to produce separate echoes is _______________ resolution
axial
The _______________ resolution is the ability to produce separate echoes perpendicular to the sound path; it is affected by transducer diameter and focusing.
lateral
Lateral resolution is determined by _______________.
beam width
_______________ resolution refers to the ability to resolve objects that are the same distance from the transducer but are located perpendicular to the plane of imaging.
Azimuthal
Identify three criteria that determine the type of transducer selected for a particular examination.
examination, size of patient, amount of fatty or muscle tissue
The number of pulses launched per second is the _______________.
pulse repetition frequency
If the gain is set too _______________, artifactual echo noise will be displayed throughout the image.
high
A one-dimensional image displaying the amplitude strength of returning echo signals along the vertical axis and the time (distance) along the horizontal axis is produced by _______________.
amplitude modulation
The intensity (amplitude) of an echo attained by varying the brightness of a dot to correspond to echo strength is displayed by the _______________ method.
brightness modulation
The condition of assigning each level of amplitude a particular shade of gray is referred to as the _______________.
gray scale
The _______________ displays time along the horizontal axis and depth along the vertical axis to depict movement, especially in cardiac structures.
motion mode
A dynamic presentation of multiple image frames per second over selected areas of the body is provided by _______________ imaging.
real-time
With pulsed Doppler, for accurate detection of Doppler frequencies, the Doppler signal must be sampled at least _______________ for each cycle in the wave.
twice
When the Nyquist limit is exceeded, an artifact called _______________ occurs.
aliasing
