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  • Sample Reports - Radiology

• MRI Terms

- A -

• AC

Alternating Current is a continuously changing flow of electrons that alternates its polarity at a periodic rate.



• ACQUISITION

The process of measuring and storing image data.



• ACQUISITION MATRIX

The total number of independent data samples in the frequency (f) and phase (f) directions.



• ACQUISITION TIME

The period of time required to collect the image data. This time does not include the time necessary to reconstruct the image. ADC analog-to-digital converter



• ALIASING (WRAP AROUND ARTIFACT)

The phenomenon resulting from digitizing fewer than two samples per period in a periodic function. Aliasing can occur in MR imaging whenever the area of anatomy extends beyond the field of view. These areas extending beyond the field of view boundaries are aliased back into the image to appear at artifactual locations.



• ALTERNATING CURRENT (AC)

A current that continuously changes in magnitude and direction. In the US the current changes at a frequency of 60 Hz.



• AMPLITUDE

The signal height. The greater the amplitude of the signal, the larger the number of protons in the image and the brighter it will appear.



• ANALOG

Being continuous, or having a continuous range of values.



• ANALOG-TO-DIGITAL CONVERTER (ADC)

A system that receives analog input data and produces digital values at its output. Used by the MRI scanner to convert the received signal into a format more compatible with the computer systems.



• ANTENNA

A device that enables the sending and/or receiving of electromagnetic waves. See also Transmitter, Receiver Coils and Surface Coils.



• ARCHIVING

The storage of image and patient data for future retrieval.



• ARRAY PROCESSOR

A dedicated computer system used to perform Fourier transformations to accelerate the processing of the received numerical data relative to the MR imaging process.



• AVERAGING

See Signal Averaging.



• AXIAL

A plane, slice or section made by cutting the body or part of it at right angles to the long axis. If the body or part is upright, the cut would be parallel to the horizon. B or Bo - a conventional symbol for the constant magnetic field produced by the large magnet in the MR scanner. B1 - the conventional symbol used for identifying the radio frequency (RF) magnetic field.