Interaction between a spin and its neighbors due to their magnetic dipole moments. This is an important mechanism contributing to relaxation rates. In solids and viscous liquids this can result in broadening of the spectral lines.

(DE FGR) A gradient echo sequence using a pulse, which sensitizes the sequence to variations in T2, rather than waiting for T1 relaxation.
See Driven Equilibrium, Gradient Recalled Echo Sequence and Steady State Free Precession.

Eovist® (other brand name Primovist™) is a organ specific MRI contrast agent for the imaging, detection and characterization of liver conditions, including liver tumors, cysts, as well as other malignant and benign lesions. It is a water-soluble ethoxybenzyl derivative of Gd-DTPA. This compound is taken up by the hepatocytes (approximately 30% of the dose goes to the hepatocytes) and is equally excreted renal and biliary in humans. Excretion of Gd-EOB-DTPA in the bile may also permit visualization of both the gall bladder and the bile ducts.
Eovist® brightens the signal of T1 weighted MR images immediately after contrast administration. Dynamic and accumulation phase imaging can also be performed after bolus injection of Eovist®. The hepatocytes uptake will increase the signal intensity of normal liver parenchyma at 10 to 20 minutes after injection. This results in improved lesion-to-liver contrast because malignant tumors (metastases, the majority of hepatocellular carcinomas) do not contain either hepatocytes or their functioning is hampered.

WARNING: Gadolinium-based contrast agents increase the risk for nephrogenic systemic fibrosis (NSF) in patients with acute or chronic severe renal insufficiency (glomerular filtration rate less than 30 mL/min/1.73m²), or acute renal insufficiency of any severity due to the hepato-renal syndrome or in the perioperative liver transplantation period.

See also Drug Development and Approval Process USA, Contrast Medium, Hepatobiliary Contrast Agents, Tumor Specific Agents and Molecular Imaging.

Motion of material being imaged, particularly flowing blood, can result in many possible effects in the images.
Fast moving blood produces flow voids, blood flowing in to the outer slices of an imaging volume produces high signals (flow related enhancement, entry slice phenomenon), pulsatile flow creates ghost images of the vessel extending across the image in the phase encoding direction (image misregistration).
Flow-related dephasing occurring when spin isochromats are moving with different velocities in an external gradient field G so that they acquire different phases. When these phases vary by more then 180° within a voxel, substantial spin dephasing results leading to considerable intravascular signal loss.
These effects can be understood as caused by time of flight effects (washout or washin due to motion of nuclei between two consecutive spatially selective RF excitations, repeated in times on the order of, or shorter than the relaxation times of blood) or phase shifts (delay between phase encoding and frequency encoding) that can be acquired by excited spins moving along magnetic field gradients.
The inconsistency of the signal resulting from pulsatile flow can lead to artifacts in the image. The flow effects can also be exploited for MR angiography or flow measurements.

See also Flow Artifact.

(FRE) Flow related enhancement could be seen most for blood flow, but also for other liquids with some MR imaging techniques, as an increase in intensity due to the washout of saturated spins. FRE provides positive contrast ("bright blood") of vascular details in time of flight MRA as well as the physiologic characterization of blood flow.
If stationary spins within the scanned region experience only an incomplete T1 relaxation between the repeated radio frequency (RF) excitations, this results in fewer signal of the stationary tissue (compared to inflowing blood with completely relaxed spins). The degree of the flow related enhancement is proportional to the blood flow velocity and the used repetition time. The use of flow compensation (gradient moment nulling) improves the FRE especially in gradient echo sequences.