Cha 1 Foundations of Sonography Flashcards
Acoustic impedance
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
angle of incidence
Angle at which a sound beam strikes the interface between two types of tissue
attenuation
Reduction in amplitude and intensity of a sound wave as it propagates through a medium
axial resolution
Refers to the minimum distance between two structures positioned along the axis of the beam where both structures can be visualized as separate objects
compression
region of increased particle density
crystal
Special material in the transducer that has the ability to convert electric impulses onto sound waves
decibel
Unit used to quantitatively express the ratio of two amplitudes or intensities
focal zone
Region over which the effective width of the sound beam is within some measure of its width at the focal distance
frequency
Number of cycles per second that a periodic events or function undergoes
intensity
Power per unit area
interface
Surface forming the boundary between media having diffeent properties
megahertz (MHz)
1,000,000Hz
piezoelectric
Generation of electric signals as the result of an incident sound beam on a material that has piezoelectric properties
power
Rate of energy flow over the entire beam of sound
refraction
Change in the direction of propagation of a sound wave transmitted across an interference where the speed of sound varies
resolution
Ability of the transducer to distinguish between two structures adjacent to one another
transducer
Any device that convert energy from one form to another
wave
Propagation of energy that moves back and fourth or vibrates at a steady rate
wavelength
Distance over which a wave repeats itself during one period of oscillation
resistance
Passive force in opposition to another, active force; when tissue exert pressure against the flow
angle of reflection
Angle of incidence at which the sound beam strikes the interface
velocity
Speed of the ultrasound wave;determined by tissue density
cycle
Sequence of events occurring at regular intervals
Fraunhofer zone
Field farthest from the transducer during formation of the sound beam
hertz Hz
Unit for frequency; equal to 1 cycle per second
kilohertz kHz
1000Hz
lateral resolution
Minimum distance between two objects at which they still can be displayed as separate objects
pulse duration
Time interval required for generating the transmitted pulse
Fresnel zone
Field closet to the transducer during formation of the sound beam
slice thickness
Thickness of the section in a patient that contributes to echo signals on any one image
aliasing
Technical artifact that occurs when the frequency change is so great that it exceeds the sampling view and pulses repetition frequency
amplitude
Strength of the ultrasound wave measured in decibels
continuous wave (CW) Doppler
One transducer continuously transmits sound and one continuously receives sound; used in high velocity flow patterns
Doppler angle
Angle that the reflector path makes with the ultrasound beam; the most accurate velocity is recorded when the beam is parallel to flow
Doppler shift
Change in frequency of a reflected wave; cause by motion between the reflector and the transducer’s beam
dynamic range
Ratio of the largest to the smallest signals that an instrument or a component of an instrument can respond to without distortion
frame rate
Rate at which images are updated on the display;dependent on transducer frequency and depth selection
gain
Measure of strength of the ultrasound signal
gray scale
B-mode scanning technique that permits the brightness of the B mode dots to be displayed in various shades of gray to represent different amplitudes
laminar
Normal pattern of vessel flow; flow in the center of the vessel in faster than it is at the edge
Nyquistsamping limit
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
pulse repetition frequency (PRF)
In pulse echo instruments, it is the number of pulses launched per second by the transducer
pulsed wave (PW) Doppler
Sound transmitted and received intermittently with one transducer
real time
Ultrasound instrumentation that allows the image to be displayed many times per second to achieve a “real time” image of anatomic structure and their motion patterns
spectral analysis
Analysis of the entire frequency spectrum
spectral broadening
Echo fill in of the spectral windows that is proportional to the severity of stenosis
temporal resolution
Ability of the system to accurately depict motion
time gain compensation (TGC)
Ability to compensate for attenuation of the transmittal beam as the sound wave travels through tissue in the body
gate
Sample site from which the signal is obtained with pulsed Doppler
frequency shift
Amount of change in the returning frequency compared with transmitting frequency when the sound waves hits a moving target such as blood in an artery
Acoustics is the study of ____, _____, and ___ sound waves.
generation, propagating, receiving
Ultrasound is defined as sound frequencies beyond the upper limits of human hearing, that is , greater than ____.
20 kilohertz
Name three pioneers who made a significant contribution to ultrasound
Donald Baker, Hertz and Inge Edler, William Fry, Joseph Holmes, Douglass Howry, George Ludwig, Robert Rushmer, John Wild
The terms ___, ____, and ____ have all been used to describe a imaging technique by which soft tissue structure 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 ____.
echocardiograpghy
One who preforms ultrasound studies and gather diagnostic data under the direct or indirect supervision of a physician is a ___.
sonographer
List the qualities of a good sonograher
Good physical health, emotional stability, communication skills, dedication, independence, ability to conceptualize two dimensional image into 3, intellectual curiosity
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 fourth or vibrates at a steady rate is a ____.
waves
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 ___ 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 are is defined as ____.
intensity
If you double the power, the intensity ____.
Double
The piezoelectric effect was first described by the _____ brother in 1880
Curie
Air-filled structures, such 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 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 echos is _____ resolution
axial
The ____ resolution refers to 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 3 criteria that determine the type of transducer selected for a particular examination
examination, size of patient, and amount of fatty or muscular tissue present
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 dynamic presentation of multiple image frames per second over selected area of the body is provided by ___ imaging
real time
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______.
amplitudes modulation
The intensity (amplitude) of an echo attained by varying the brightness of a dot 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 the time along the horizontal axis and depth along the vertical axis to depict movement, especially in cardiac structures
motion mode
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
