Spin dephasing for complex flow patterns like turbulence. This effect must be taken into account when evaluating the extent of vascular stenosis. The degree of the signal loss depends on the flow model and pulse sequence used.

A differential equation expresses a relationship between functions and their derivatives. In MRI, the Bloch equation for example is based on this mathematical function.

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.

(TD) The difference in time between radio frequency spin echo (TER) and gradient echo (TE) when the RF and gradient echoes are not coincident.

See Flow Related Enhancement.