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.

Volumetric imaging is a 3D technique where all the MRI signals are collected from the entire tissue sample and imaged as a whole entity, therefore providing a high signal to noise ratio. The acquisition of isotropic voxels or thin slices with high spatial resolution allows to create multiplanar reconstructions in all planes; a compensation for the usually longer scan time. The acquisition time can be reduced by parallel imaging technique.
New T2 weighted variants of 3D sequences (FSE-XETA, T2-SPACE, VISTA) have been introduced that differ from conventional FSE sequences. An echo train containing up to 200 echoes obtained at a minimum echo spacing allows very fast acquisition. A flip angle modulation (flip angle sweep - FAS) during the FSE readout carries magnetization as long as possible to avoid blurring and provide optimal signal at the effective echo time. This type of imaging is well suited for brain and spine MRI procedures.
Newer T1 weighted variants include Liver Acquisition with Volume Acquisition (LAVA) and T1W High Resolution Isotropic Volume Examination (THRIVE), which have advantages for dynamic breath hold imaging in liver and abdominal examinations.

See also Volume Imaging, 3 Dimensional Imaging.