Ultrasound Terminology Flashcards
What is acoustic pressure?
The value of the total pressure mins the ambient pressure.
What is an amplitude modulated waveform?
The value of the expression 100 x (|A|-|B|) /|A| where |A| and |B| are the absolute maximum and absolute minimum values of the envelope of a modulated acoustical or electrical carries (first order quantity), respectively, expressed as a percentage.
What is an anechoic material?
Acoustic absorbing material that exhibits no reflective properties.
What is auto-scan (auto scanning)?
The electronic or mechanical steering of successive ultrasonic pulses or series of pulses, through at least 2 dimensions
What is bandwidth?
The difference in frequencies f1 and f2 at which the transmitted acoustic pressure spectrum is 71% (-3dB) of it maximum value
What is the beam axis?
A straight line joining the points of maximum pulse intensity integral measured at several distances in the far field. This line, calculated according to regression rules, is to be extended back to the transducer assembly surface
What is the beam cross-sectional area?
The area on the surface of a plane perpendicular to the beam axis consisting of all points where the pulse intensity integral is greater than 25 percent of the maximum pulse intensity integral in that plane. For situations in which the relative pressure waveform does not change significantly across the beam cross-sectional area, the beam cross-sectional area may be approximated by measuring the area on the surface of a plane perpendicular to the beam axis consisting of all points where the acoustic pressure is greater than 50% of the maximum acoustic pressure in the plane.
What is a broadband producer?
A transducer with a fractional bandwidth greater than or equal to 15%
What is the centre frequency?
fc is (f1 + f2) / 2 where f1 and f2 are frequencies defined in bandwidth
What is a centroid?
A surface is the point whose coordinates are the mean values of the coordinates of a representative sample of all points on the surface
What is combined mode? (combined operating mode)
It is any combination of two or more of the discrete operating modes operating simultaneously
What is a continuous waveform?
A waveform in which the amplitude modulation factor in which a continuous waveform is generated
What is CW doppler? (Continuous-wave doppler)
A discrete operating mode in which continuous waveform is generated
What is energy fluence?
The acoustic energy transmitted in the direction of acoustic wave propagation, per unit area normal to this direction, at the point considered during a given time period. It is equal to the time integral of the instantaneous intensity during the same period.
What is Energy fluence per pulse?
The energy fluence during the duration of a single pulse. It is equal to the pulse intensity integral
