AACE Glossary Flashcards
Acoustic Power with units
Quantity if energy generated by the transducer, in watts
Acoustic scattering
Reflections from small objects size of wavelength or smaller
Acoustic Shadow
Loss of echo signals from distal structures due to attenuation of overlying structures.
Acoustic velocity
The speed of sound through a medium as determined by the stiffness and density of the medium.
Aliasing
Technical artifact occurring when the frequency change is so large it exceeds the sampling view and pulse repetition frequency. The frequency display wraps around so that the signal is seen at both the top and bottom of the image.
Amplitude with units
Strength or height of wave, measured in decibels.
Amplitude mode (A-mode)
One- dimensional image displaying amplitude of returning echo signals on vertical axis and time (distance from transducer) on horizontal axis.
Anechoic
No echoes.
Eg. Cysts, gall-bladder etc
Attenuation
Reduction in intensity and amplitude with increasing distance traveled due to scatter, reflection and absorption.
Axial resolution
Depth resolution; ability to separate two objects lying in tandem along axis of beam.
Azimuthal
The dimension perpendicular to the image slice, the thickness of the slice of anatomy.
Bandwidth
The frequency range represented in a pulse from the transducer.
B-scan
Two-dimensional cross sectional image displayed on a screen in which brightness of echoes and their position on the screen are determined by the movement of a transducer and the time it takes the echoes to return to the transducer.
Cineloop
System memory stores most recent sequence of images in a series of frames before the freeze button is pressed allowing a continuous loop if images to be reviewed.
Color flow Doppler
Operating mode - two-dimensional image generated that portrays moving reflectors in color simultaneously with B-mode images.
Complex
Heterogenous structure which may have both cystic and solid components.
Compression
Regions of high pressure and density as sound travels through a medium.
Crystal
The active transducer component that actually generates and receives ultrasonic energy by converting electrical impulses into sound waves and vice versa.
Cystic
Sac or pouch with definite wall containing fluid or semi-solid material.
Decibel (db)
Unit for intensity of sound waves
Density
Concentration of matter (mass per unit volume)
Doppler shift
Perceived frequency change that occurs dependent upon whether the source and listener are moving towards or away from each other.
Dynamic range
Range of intensity from the largest to smallest echo that the system can display (log compression).
Echo
Reflected sound
Echogenic
Capable of producing echoes
Echopenic
Few echoes within a structure; less Echogenic
Echolucent
Without internal echoes; anechoic
Edge enhancement
Electric post-processing function which makes contours of structures within the image more distinct and clear.
Electronic focusing
Each crystal element within a group is pulsed separately to focus the beam at a particular area of interest.
Enhancement
Structures distant to cystic lesion appear to have more echoes because sound is barely attenuated through fluid-filled structure.
Far gain
Control affecting strength of distant echoes in the image
Focal zone
Depth of sound beam where resolution is highest.
Focusing
The act of narrowing the beam to a small width at a set depth.
Footprint
Shape of the transducer that is in contact with the patient.
Frame rate
Rate at which the image is refreshed in a real-time system display.
Frequency
Number of times in a given interval a particles action occurs.
Gain
Regulates the brightness of returning echoes to compensate for loss of transmitted sound caused by absorption and reflection.
Gray scale
Display mode in which echo intensity is recorded as degrees of brightness or shades of grey.
Hertz
Unit for wave frequency (cycles per second); pulse repetition frequency (pulses per second); frame rate (frames per second)
Heterogeneous
Uneven echo pattern or reflection of varying echo densities
Homogenous
Even echo pattern or reflections that are relative and uniform in composition.
Hyperechoic
Structure produces stronger echo than surrounding structures
Hypoechoic
Structures with weaker echoes than surrounding tissues
Interface
Surface forming the boundary between media having different properties
Isoechoic
Structure that produces echo of same strength as surrounding structures.
Kilohertz
1000 hertz
Lateral resolution
Ability to separate two objects that are positioned perpendicular to the axis of the ultrasound beam.
Linear array
Many small electronically coordinated transducers producing a rectangular image.
Megahertz
1,000,000 hertz
Near gain
The application of echoes returning from the near field.
Noise
Artificial echoes resulting from too much gain rather than echoes from true anatomic structures.
Overall gain control
Single gain control that increases amplification at all depths.
Phased array
Electronically steered system where many small transducers are electronically coordinated to produce a focus wave front.
Piezoelectric effect
Electric current created by pressure forces. Certain ceramic materials can convert pressure to electricity.
Persistence
The accumulation of echo information over a specified period of time.
Power Doppler
The presentation of two-dimensional Doppler information by color-encoding the strength of the Doppler shifts. Power Doppler is free of aliasing and angle dependence and is more sensitive to slow flow and flow in small or deep vessels.
Pulse-echo Principal
Sending pulses of ultrasound into the body so that they react with tissue and return reflections.
Pulse Repetition Frequency (PRF)
The number of times per second that a transmit-receive cycle occurs.
Refraction
Bending of waves as they pass from one medium to another
Resolution
Ability to distinguish between two adjacent structures (interfaces)
Reverberation
The phenomenon of multiple back-and-forth reflections created by two strong reflectors that causes the echoes to be misplaced in the display thereby representing a false image
Scattering
Redirection of ultrasound from a reflector which is small compared to the wave length of the beam. Occurs with rough surfaces or heterogeneous areas.
Shadowing
Failure of sound beam to pass through an object
Slice thickness
Elevational resolution.
The size of the beam perpendicular to the image plane.
Sonodense
Structure that transmits sound poorly
Spatial resolution
How closely positioned two reflectors can be to one another and still be identified as separate reflectors on an image display.
Speckle
Interference effects of the scattered sound from the distribution of scatterers in the tissue that is not related to the scattering properties of tissue. Produces granular appearance.
Specular reflectors
Reflection from smooth surfaces compared to the wavelength of sound thereby creating a bright echo on the monitor.
Stiffness
Resistance of a material to compression
Temporal resolution
The ability of a display to distinguish closely spaced events in time and to present rapidly moving structures correctly.
Improves with frame rate.
Texture
The echo pattern of an organ
Time gain compensation or depth gain compensation
Control that compensates for the loss (attenuation) of the sound beam as it passes through tissue.
Transducer
An electromechanical device - coverts electrical every to mechanical energy and vice versa.
Wavelength
Distance wave travels in a second
What happens to wavelength if frequency increases?
Becomes smaller
Acoustic impedance
Density x velocity of sound in a particular material
Amount of reflection of sound beam depends of differences in the impedances if two tissues
