Sonography Terms

Dynamic Range

(Log Compression). The range of intensity from the largest to the smallest echo that the system can display.

Amplitude Mode (A-Mode)

A one-dimensional image displaying the amplitude strength of the returning echo signals along the vertical axis and the time (the distance from the transducer) along the horizontal axis.

Cystic

A sac or pouch with a definite wall that contains fluid or semisolid material

Aliasing

A technical artifact occurring when the frequency change is so large that 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.

B-Scan

A two-dimensional cross-sectional image displayed on a screen in which the 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. Also, static scan.

Decibel (db)

A unit used to express the intensity of amplitude of sound waves; does not specify voltage.

Edge Enhancement

An electronic postprocessing function which makes contours of structures within the image more distinct and clear.

Enhancement

Because sound traveling through a fluid-filled structure is barely attenuated, the structures distal to a cystic lesion appear to have more echoes than neighboring areas. Also called through transmission.

Echogenic

Capable of producing echoes. Correlate with the terms hyperechoic, hypoechoic, and anechoic, which refer to the quantity of echoes produced.

Density

Concentration of matter (mass per unit of volume)

Far Gain

Control that affects the strength of the distant echoes in the image.

Axial Resolution

Depth resolution; ability to separate two objects lying in tandem along the axis of the beam. Lie parallel.

Gray Scale

Display mode in which echo intensity is recorded as degrees of brightness or shades of gray.

Electronic Focusing

Each crystal element within a group is pulsed separately to focus the beam at a particular area of interest

Echopenic

Few echoes within a structure; less echogenic. Echo-poor.

Acoustic Shadow

Loss of echo signals from distal structures due to attenuation of overlying structures.

Color Flow Doppler

Operating mode in which a two-dimensional image is generated that portrays moving reflectors in color simultaneously with B-mode images.

Acoustic Impedance Meaning

Product of density and velocity of sound in a particular material. The amount of reflection of a sound beam is determined by the difference in the impedances of the two tissues.

Acoustic Power

Quantity of energy generated by the transducer, expressed in watts. Also transmit power.

Frame rate

Rate at which the image is refreshed in a real-time system display.

Attenuation

Reduction in amplitude and intensity with increasing distance traveled due to scattering, reflection, and absorption. Dependent on frequency, higher frequencies give less penetration.

Complex

Refers to a heterogeneous structure that may contain both cystic (fluid-filled) and solid components.

Homogeneous

Refers to an even echo pattern or reflections that are relative and uniform in composition.

Heterogeneous

Refers to an uneven echo pattern or reflections of varying echo-densities.

Anechoic

Refers to structure that returns no echoes. This could be a simple cyst or cystic structure such as the gall bladder, urinary bladder, or chambers of the heart. Also, sonolucent, echo-free, echolucent, transonic.

Echo

Reflected sound

Acoustic Scattering

Reflections from small objects that are the size of the wavelength or smaller. The bowel gas causes scattering of the signal and loss of resolution.

Compression

Regions of high pressure and density as sound travels through a medium.

Gain

Regulates the amplification (brightness) of returning echoes to compensate for loss of transmitted sound caused by absorption and reflection.

Footprint

Shape of the transducer that is in contact with the patient.

Amplitude

Strength or height of the wave, measured in decibels.

Focusing

The act of narrowing the beam to a small width at a set depth.

Crystal

The active transducer component that actually generates and receives ultrasonic energy by converting electrical impulses into sound waves and vice versa.

Focal zone

The depth of the sound beam where resolution is the highest.

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, quality factor.

Frequency

The number of times a particular action occurs in a given interval of time.

Doppler shift

The perceived frequency change that occurs dependent upon whether the source and listener are moving toward or away from one another.

Acoustic Velocity

The speed of sound through a medium as determined by the stiffness and density of the medium. Also, speed of sound; propagation speed; sound velocity.

Cineloop

The system memory stores the most recent sequence of images in a cineloop before the freeze button is pressed. A continuous loop of 16 to 64 images can be reviewed.

Hertz

Unit for frequency (cycles per second); pulse repetition frequency (pulses per second); frame rate (frames per second).

Echolucent

Without internal echoes, anechoic