Anti aliasing is a method to prevent aliasing artifacts by properly choosing the sampling rate. The signal is sampled at a higher bandwidth than required.

See Oversampling.

The Dixon technique is a MRI method used for fat suppression and/or fat quantification. The difference in magnetic resonance frequencies between fat and water-bound protons allows the separation of water and fat images based on the chemical shift effect.
This imaging technique is named after Dixon, who published in 1984 the basic idea to use phase differences to calculate water and fat components in postprocessing. Dixon's method relies on acquiring an image when fat and water are 'in phase', and another in 'opposed phase' (out of phase). These images are then added together to get water-only images, and subtracted to get fat-only images. Therefore, this sequence type can deliver up to 4 contrasts in one measurement: in phase, opposed phase, water and fat images. An additional benefit of Dixon imaging is that source images and fat images are also available to the diagnosing physician.
The original two point Dixon sequence (number of points means the number of images acquired at different TE) had limited possibilities to optimize the echo time, spatial resolution, slice thickness, and scan time; but Dixon based fat suppression can be very effective in areas of high magnetic susceptibility, where other techniques fail. This insensitivity to magnetic field inhomogeneity and the possibility of direct image-based water and fat quantification have currently generated high research interests and improvements to the basic method (three point Dixon).
The combination of Dixon with gradient echo sequences allows for example liver imaging with 4 image types in one breath hold. With Dixon TSE/FSE an excellent fat suppression with high resolution can be achieved, particularly useful in imaging of the extremities.
For low bandwidth imaging, chemical shift correction of fat images can be made before recombination with water images to produce images free of chemical shift displacement artifacts. The need to acquire more echoes lengthens the minimum scan time, but the lack of fat saturation pulses extends the maximum slice coverage resulting in comparable scan time.

The quality of magnetic resonance imaging is particularly dependent on image resolution (matrix, field of view, slice thickness), contrast (TE, TR), signal to noise ratio (bandwidth, signal averaging) and lack of artifacts. These MRI parameters are affected by the field homogeneity, the field strength, the coil, the pulse sequence type and imaging techniques like parallel imaging.

See also Image Contrast Characteristics.

(MEDIC) MEDIC is a heavily T2* weighted spoiled gradient echo sequence with multiple echoes. MEDIC uses a series of identically phase encoded gradient echoes, sampled per line in k-space. Unipolar frequency encoding gradients are used to achieve flow compensation and to avoid off resonance effects. For each echo the magnitude images are reconstructed and postprocessed by using a sum of squares algorithm to improve the signal to noise ratio. The increased receiver bandwidth reduces the T2* effects and impairment of the spatial resolution.
The multi echo data image combination sequence is potentially useful in imaging of cartilage in joints.

(PE) The partial echo technique (also called fractional echo) is used to shorten the minimum echo time. By the acquisition of only a part of k-space data this technique benefits (like all partial Fourier techniques) from the complex conjugate symmetry between the k-space halves (this is called Hermitian symmetry).
The dephasing gradient in the frequency direction is reduced, and the duration of the readout gradient and the data acquisition window are shortened. Partial echo gives a better SNR at a given TE when a smaller FOV or thinner slices are selected, allows a longer sampling time, and a larger water fat shift (WFS, see also bandwidth) due to a lower gradient amplitude. The resolution is not affected. This is often used in gradient echo sequences (e.g. FLASH, Contrast Enhanced Magnetic Resonance Angiography) to reduce the echo time and yields a lower gradient moment. The disadvantage of using a partial echo can be a lower SNR, although this may be partly offset by the reduced echo time.
Also called Fractional Echo, Read Conjugate Symmetry, Single Side View.

See also Partial Fourier Technique and acronyms for 'partial echo' from different manufacturers.