The k-space is an extension of the concept of Fourier space that is well known in imaging. In MR imaging the k-space is a temporary memory of the spatial frequency information in two or three dimensions of an object; the k-space is defined by the space covered by the phase and frequency encoding data.
The relation between K-space data and image data is the Fourier Transformation. The data acquisition matrix contains raw image data before the image processing. In 2 dimensional Fourier transformation imaging, a line of data corresponds to the digitized MRI signal at a particular phase encoding level. The position in k-space is directly related to the gradient across the object being imaged. By changing the gradient over time, the k-space data are sampled in a trajectory through Fourier space at each point until it is filled.

See also Spatial Frequency and Raw Data.

The number of data points collected in one, two or all three directions. Normally used for the 2D in plane sampling. The display matrix may be different from the acquisition matrix, although the latter determines the resolution. Measurement time may be saved by not acquiring raw data lines corresponding to high resolution. Not measured rows are filled with zeroes prior to the image calculation. A square image is the result of an interpolation in phase encoding direction. See also Zero Filling.

The chosen matrix size effects scan time, resolution and SNR. Reduced measurement matrixes decrease the scan time and the resolution by increased SNR.

(MLSI) Variations of sequential line imaging techniques that can be used if selective excitation methods that do not affect adjacent lines are employed. Adjacent lines are imaged while waiting for relaxation of the first line toward equilibrium, which may result in decreased image acquisition time. A different type of MLSI uses simultaneous excitation of two or more lines with different phase encoding followed by suitable decoding.

(MY) Dimension in the stationary (laboratory) frame of reference in the plane orthogonal to the direction of the static magnetic field (B0 and H0), z, and orthogonal to x, the other dimension in this plane. This is commonly defined to be in the direction of the phase encoding gradient.

The navigator technique measures with an additional quick MR prepulse the position, of e.g. the diaphragm before data collecting. Similar respiratory conditions of the patient can be identified and used to synchronize image data acquisition so that respiration induced image blurring is minimized by either respiratory ordered phase encoding or respiratory gating.
The prepulse sequence images a small area perpendicular to the structure, which is moving. The contrast of the interface between the diaphragm and the lung should be high to permit easy automatic detection. After data acquisition, the position of the interface is automatically recorded and imaging data are only accepted when the position of the interface falls within a range of prespecified values.
This technique has the advantage of greater accuracy than other respiratory gating (therefore used for coronary angiography) and has no need for additional sensing MRI equipment, as the MR system itself provides it.