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Definition
| The transfer of ultrasound energy to the tissue during propagation. |
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Definition
| The product of the density of the medium and the velocity of sound; differences in AI between 2 media determine the ratio of transmitted versus reflected sound at the interface. |
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| The magnitude of the pressure changes along the wave; also, the strength of the wave (in decibels) |
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Definition
| The net loss of ultrasound energy as a wave propagates through a medium. |
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| the ability to differentiate two structures lying along the axis of the ultrasound beam (i.e. one behind the other)pg. |
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| widening of the ultrasound beam at a given distance. Where the beam becomes cone shaped. |
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| provides information on instantaneous pressure gradient. |
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| The combination or sum of 1 compression and 1 rarefaction of a propagating wave. |
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Definition
| The time in between pulses that the echograph is not emitting ultrasound. |
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| A logarithmic measure of the intensity of sound, expressed as a ratio to a reference value (dB) |
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Definition
| compensates for the loss of ultrasonic energy (i.e. attenuation) as the beam propagates through the body. The primary purpose is to enhance the far echoes and suppress near echoes, without creating distortion or artifact. |
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Definition
| The fraction of time that the transducer is emitting ultrasound, a unitless number between 0 and 1. |
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Definition
| The diverging conical portion of the beam beyond the near field. |
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Definition
| The number of cycles per second, measured in Hertz (Hz). |
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Definition
| The diverging conical portion of the beam beyond the near field. |
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Definition
| the part of the beam closest to the transducer and parallel to it. (WB P.5)the proximal or cylindrical portion of the beam(HF p.16)signal. |
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Definition
| The distance an ultrasound beam penetrates into a medium before its intensity has attenuated to one-half the original value. |
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Definition
| The amplitude, or the degree of amplification, of the received signal. |
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Definition
| The concentration or distribution of power within an area, often the cross-sectional area of the ultrasound beam, analogous to loudness. |
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Definition
| A plane or other surface forming a common boundary of two bodies or spaces. Also, the plane at which sound leaves one medium and enters the tissue of a different medium. |
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Definition
| the resolution that is perpendicular to the u/s beam on an X and Y-axis. (WB p.6) the ability to distinguish two reflectors that lie side by side relative to the beam (HF p.19) |
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Definition
| A cyclic disturbance in which the energy propagation is parallel to the direction of particle motion. |
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Definition
| the upper limit of frequency that can be detected within a given pulsed system-the limit at which aliasing occurs. Defined as one-half PRF. |
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Definition
| The time required to complete 1 cycle, usually expressed in microseconds. |
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Definition
| a transducer, which consists of multiple small elements fired individually in a controlled manner. (WB p.14) which consist of a series of small piezoelectric elements interconnected electronically. By manipulating the timing of excitation of individual elements, both focusing and steering are possible. (HF p.17) |
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Definition
| The phenomenon of changing shape in response to an applied electric current, resulting in vibration and the production of sound waves; the ability to produce an electric impulse in response to a mechanical deformation; thus, the interconversion of electrical and sound energy. |
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Definition
| The rate of transfer over time of the acoustic energy from the propagating wave to the medium, measured in Watts. |
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Definition
| time required for the peak pressure gradient to be reduced by one-half. |
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Definition
| A burst or packet of emitted ultrasound of finite duration, containing a fixed number of cycles traveling together. |
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Definition
| The physical length or distance that a pulse occupies in space, usually expressed in millimeters (mm). |
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Definition
| the repetition rate of the ultrasound pulse, also known as the sampling rate. |
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Definition
| the expansion of a piezoelectric crystal after compression (WB p. 15) sine wave whose peaks and troughs correspond to areas of compression and rarefaction, respectively. (HF p. 11, 12) |
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Term
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Definition
| the continuing of an u/s beam particle in a different direction at an area of acoustical interface (WB p.15) the transmitted portion of the energy is refracted, or bent, depending on the angle of incidence and differences in impedance between the tissues. (HF p. 14 Fig 2.2) |
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Definition
| the reflection in a continuous manner as a series echo. Artifacts appear when the sound and the original interface thus, producing a false impression of additional interfaces at multiples of the original transducer interface distance. (WB p. 16) One or more echo targets directly behind the reflector. (HF p. 30) |
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Definition
| echoes returning to the transducer because of acoustic impedance. |
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Definition
| Low end, noise and undesired weak echoes exist that can be eliminated using a reject control. |
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Definition
| the ability to distinguish between two objects in close proximity. |
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Definition
| The ability of the system to image small targets at a given depth. |
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Definition
| selectively amplifying echoes from greater depths, using a method referred to as time gain compensation, images of uniform brightness are created. Allows returning signals from different depths to be selectively suppressed or amplified to provide relatively uniform signal strength. |
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Definition
| The speed at which sound moves through a given medium. |
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Definition
| The length of a single cycle of the ultrasound wave; a measure of distance, not time. |
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