Bipolar gradients are two gradients with the same magnitude but opposite gradient direction. A bipolar gradient pulse is produced if one of the bipolar gradients is switched e.g., in negative direction and then switched in the opposite direction for an equivalent amount of time.
Bipolar gradients are used e.g. in phase contrast and diffusion weighted sequences. A bipolar gradient pulse pair produces a phase shift, which depends on the velocity component along this gradient. Motion along a bipolar gradient pulse pair results in a flow-induced phase shift of the transverse magnetization. The bipolar gradient pulse pair will not affect stationary spins. The amount of phase shifts depends on the area of each gradient pulse, and distance between the pulses. An echo occurring after such a gradient is flow compensated for velocity. A slight shift in the balance of this gradient will introduce a defined flow sensitivity of the pulse sequence.

Short name: CMC 001, central moiety: Mn2+
CMC 001 is an orally administered MRI contrast agent in development for enhancement of the liver, bile ducts and gastrointestinal tract. Applications are screening of liver tumors/metastases, imaging of the biliary tract and it could be suitable for liver function studies by following the metabolism and excretion of manganese in the liver cells. Several advantages like better images, higher safety, lower costs and less inconvenience for the patient can be expected.
Animal experiments and clinical studies in humans Phase I and Phase II A, have shown excellent contrast enhancing properties with only minimal adverse effects. CMC 001 is under development by the Medicon Valley based CMC Contrast AB to receive a cost effective, safe and highly diagnostic MR contrast medium for abdominal MR imaging. Clinical studies in Phase III are started.

Quick Overview

Pulsatile cerebro spinal fluid flow produces ghost artifacts that are superimposed in the image.

Flow compensation should be used to reduce these artifacts. This applies an additional gradient to eliminate phase differences for both stationary and moving spins at the echo time. At TE no phase differences is measured. If flow compensation is applied and there are still flow artifacts, cardiac triggering is an additional option to reduce these artifacts.
See also Motion Artifact.

A state of a spin sample in which all spins in a voxel are in phase.

(CRISP) A specific pulse sequence, wherein the application of strategic gradient pulses can compensate for the objectionable spin phase effects of flow motion.