(DWI) Magnetic resonance imaging is sensitive to diffusion, because the diffusion of water molecules along a field gradient reduces the MR signal. In areas of lower diffusion the signal loss is less intense and the display from this areas is brighter. The use of a bipolar gradient pulse and suitable pulse sequences permits the acquisition of diffusion weighted images (images in which areas of rapid proton diffusion can be distinguished from areas with slow diffusion).
Based on echo planar imaging, multislice DWI is today a standard for imaging brain infarction. With enhanced gradients, the whole brain can be scanned within seconds. The degree of diffusion weighting correlates with the strength of the diffusion gradients, characterized by the b-value, which is a function of the gradient related parameters: strength, duration, and the period between diffusion gradients.
Certain illnesses show restrictions of diffusion, for example demyelinization and cytotoxic edema. Areas of cerebral infarction have decreased apparent diffusion, which results in increased signal intensity on diffusion weighted MRI scans. DWI has been demonstrated to be more sensitive for the early detection of stroke than standard pulse sequences and is closely related to temperature mapping.
DWIBS is a new diffusion weighted imaging technique for the whole body that produces PET-like images. The DWIBS sequence has been developed with the aim to detect lymph nodes and to differentiate normal and hyperplastic from metastatic lymph nodes. This may be possible caused by alterations in microcirculation and water diffusivity within cancer metastases in lymph nodes.

See also Diffusion Weighted Sequence, Perfusion Imaging, ADC Map, Apparent Diffusion Coefficient, and Diffusion Tensor Imaging.

(GRASE) A hybrid sequence with a combination of gradient and spin echo sequences. If multiple image lines are obtained during a single echo, the imaging pulse sequence type is a GRASE sequence.

See Gradient Echo Sequence and Spin Echo Sequence.

(LAVA) The MRI technique LAVA is based on a 3 dimensional spoiled gradient echo pulse sequence. The optimized inversion pulse and a new fat suppression technique (called segmented special) provides enhanced image contrast and uniform fat suppression. Array spatial sensitivity encoding technique (ASSET) with partial data filling and shorter TR/TE enables to use short breath holds for dynamic liver imaging with multiple phases.

(MPGR) Multiplanar gradient recalled acquisition in the steady state is a term for a fast gradient echo sequence with slice selective RF pulses.

See Gradient Recalled Echo Sequence and Gradient Echo Sequence.

(PRESS) Point resolved spectroscopy is a multi echo single shot technique to obtain spectral data. PRESS is a 90°-180°-180° (slice selective pulses) sequence. The 90° radio frequency pulse rotates the spins in the yx-plane, followed by the first 180° pulse (spin rotation in the xz-plane) and the second 180° pulse (spin rotation in the xy-plane), which gives the signal.
With the long echo times used in PRESS, there is a better visualization of metabolites with longer relaxation times. Many of the metabolites depicted by stimulated echo technique are not seen on point resolved spectroscopy, but PRESS is less susceptible to motion, diffusion, and quantum effects and has a better SNR than stimulated echo acquisition mode (STEAM).