(Å* or A*) A unit used to measure the wavelength of X-rays.
Definition: 0.1 nanometer or 10-10 meter.

Frequency of oscillation or rotation (measured in radians/second) commonly designated by the Greek letter w; w = 2pf, where f is frequency (in hertz (Hz)).

A vector quantity given by the vector product of the momentum of a particle and its position vector. In the absence of external forces, the angular momentum remains constant, with the result that any rotating body tends to maintain the same axis of rotation. In the presence of torque applied to a rotating body in such a way as to change the direction of the rotation axis, the resulting change in angular momentum results in precession. Atomic nuclei possess an intrinsic angular momentum referred to as spin, measured in multiples of Planck's constant.

A description of the factors used in creating an image should include the type and times of the pulse sequence, the number of signals averaged or added (NSA), the size of the reconstructed region, the size of the acquisition matrix in each direction, field of view and the slice thickness; usually printed at the border of MRI pictures.

A device that enables the sending and/or receiving of electromagnetic waves.

See also Transmitter, Receiver Coil and Surface Coil.