(CISS) This gradient echo sequence is a stimulated T2 echo. Two TrueFISP sequences are acquired with differing RF pulses and than combined for strong T2 Weighted high resolution 3D images.
These TrueFISP sequences are normally affected by dark phase dispersion bands, which are caused by patient induced local field inhomogeneities and made prominent by the relatively long TR used. The different excitation pulse regimes offset these bands in the 2 sequences. Combining the images results in a picture free of banding. The image combination is performed automatically after data collection, adding some time to the reconstruction process. The advantage of the 3D CISS sequence is its combination of high signal levels and extremely high spatial resolution.
Used for, e.g. inner ear, cranial nerves and cerebellum.

See also Steady State Free Precession.

(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.