(DTI) Diffusion tensor imaging is the more sophisticated form of DWI, which allows for the determination of directionality as well as the magnitude of water diffusion. This kind of MR imaging can estimates damage to nerve fibers that connect the area of the brain affected by the stroke to brain regions that are distant from it, and can be used to determine the effectiveness of stroke prevention medications.
DTI (FiberTrak) enables to visualize white matter fibers in the brain and can map (trace image) subtle changes in the white matter associated with diseases such as multiple sclerosis and epilepsy, as well as assessing diseases where the brain's wiring is abnormal, such as schizophrenia.
The fractional anisotropy (FA) gives information about the shape of the diffusion tensor at each voxel. The FA is based on the normalized variance of the eigenvalues. The fractional anisotropy reflects differences between an isotropic diffusion and a linear diffusion. The FA range is between 0 and 1 (0 = isotropic diffusion, 1 = highly directional).
The development of new imaging methods and some useful analysis techniques, such as 3-dimensional anisotropy contrast (3DAC) and spatial tracking of the diffusion tensor tractography (DTT), are currently under study.

Rectal staging is necessary for the preoperative assessment of intra- and extramural tumor infiltration or the decision for adjuvant radio-chemotherapy. One indication of MRI with luminal contrast enhancement is small bowel enteroclysis after duodenal intubation for visualization of inflammatory bowel wall thickening and other complications.
"Double contrast" enhancement of the bowel lumen is the administration of plain water or water with methylcellulose along with heavily T2 weighted sequences or contrast enhanced T1 weighted sequences.
Several oral contrast agents have been used for small bowel MRI: Mannitol, metamucil, locust bean gum, and PEG. All provide sufficient bowel distension and homogeneity, but suffer from side effects such as diarrhea. The volume of PEG or mannitol administered must be not too large in order to achieve the best compromise between distension and acceptance by the patient.
MR colonography with positive bowel lumen enhancement requires higher concentrations of paramagnetic agents compared to the available dedicated enteral contrast agents, IV compounds are used to dope water enemas for this purpose.
Some investigators advocate negative bowel enhancement with Contrast Agents to suppress high signal bowel content in MRCP ( Magnetic resonance cholangiopancreaticography ). The use of a mixture of metamucil and 20 ml of gadolinium chelate provides good homogeneity and good tolerance without diarrhea.

MR imaging technique in which the image of an object is built up from successive planes in the object. In various schemes, the planes are selected by oscillating magnetic field gradients or selective excitation.

MR imaging techniques in which the image is built from successive point positions in the object. In various schemes, the points are isolated by oscillating magnetic field gradients (sensitive point) or shaped magnetic fields.

The use of gas as a contrast medium has significant potential to avoid limitations of conventional contrast agents. Gases can transit smaller vascular conduits and can be injected through smaller and less traumatic access systems than liquids. Highly soluble gases (such as CO2) can be imaged as a bolus. Blood is displaced by the gas, with the result of negative image contrast.
Because gases are compressible, standard liquid injectors cannot be used. The design for a gasinjector should have the option for individual adaptation of blood flow rate, vessel diameter, pulse pressure, and heart rate.