INIR Flashcards
What is acoustic pressure?
The value of the total pressure minus the ambient pressure
What is an amplitude modulated waveform?
A waveform in which the amplitude modulation factor is greater than 5 percent.
What is an anechoic material?
It is an 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 two dimensions.
What is bandwidth?
It is the different between frequencies f1 and f2 at which the transmitted acoustic pressure spectrum is 71 percent (-3dB) of its maximum.
What is the beam axis?
It is a straight line joining the point of maximum pulse intensity interval (not pressure itself but integral of pressure) measured at several different distances in the far field. This line, calculated according to regression rules, is to be extended back to the transducer assembly surface.
What is beam cross sectional area?
Area of the surface of a plane perpendicular to the beam axis consisting of all point where the pulse intensity integral is greater than 25 percent of the maximum pulse intensity integral in that plane.
In what situations can the beam cross sectional area be approximated?
For situations in which the relative pressure waveform does not change significantly across the beam cross sectional area, 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 percent of the maximum acoustic pressure in the plane
What is a broadband transducer?
A transducer with a fractional bandwidth greater than or equal to 15 percent.
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 where the points whose coordinates are the mean values of the coordinates of a representative sample of all the points on the surface.
What is combined mode (combined operating mode)?
Any combination of two or more of the discrete operating modes simultaneously.
What is a continuous waveform?
A waveform in which the amplitude modulation factor is less than or equal to 5 percent.
What is CW Doppler (continuous-wave Doppler)?
It is a discrete operating mode in which a continuous waveform is generated.
What is depth of focus?
For a focusing transducer assembly, it is the distance along the beam axis between two specific points p1 and p2, on opposite sides of L, the I_SPPA peak location. Here p2 is the nearest point on the far side of L at which the pulse average intensity I_PA is equal to 0.5 times I_SPPA. Similarly p1 is the point nearest L on its transducer side at which I_PA is equal to 0.5 times I_SPPA if such a point exists; if not, then p1 is at the surface of the transducer.
