Respiratory triggering is a type of respiratory motion commonly used with fast imaging techniques. Images are acquired during the expiration phase. With this type of technique, the scan time is based on the selected TR per respiratory cycle and the patient's breathing patterns.

Liver imaging with gadolinium contrast enhanced MRI is sometimes not sufficient for a reliable diagnosis of liver lesions. For this reasons, special liver Contrast agents that are targeted to the reticuloendothelial system (RES), have been developed to improve both detection and characterization of liver and spleen lesions. Reticuloendothelial Contrast Agents, as e.g. superparamagnetic iron oxides (SPIO), are taken up by healthy liver tissue but not tumors.
These RES targeted contrast agents provide a prolonged imaging window and enough time for high spatial resolution or multiple breath hold images. Reticuloendothelial contrast agents have an increased sensitivity for the detection of small liver lesions (e.g., metastases), compared with gadolinium enhanced MRI and spiral CT. At higher field strengths with an increased signal to noise ratio the susceptibility effect with iron oxide particles may be enhanced.
Other new agents (Gadobenate Dimeglumine, Gadoxetic Acid) have both an initial extracellular circulation and a delayed liver-specific uptake. Since a considerable part of these contrast agents is excreted in the bile, functional biliary imaging can diagnose biliary anomalies, postoperative bile leaks, and anastomotic strictures. Other agents, such as liposomes (with encapsulated Gd-DTPA) or DOTA complexes are in different development stages.

See also Hepatobiliary Contrast Agents, Gadolinium Oxide, Superparamagnetic Iron Oxide and Liposomes.

The resorting of data collected over several acquisitions to create an image where all phase encoding lines are acquired with the object at the same spatial location of the respiratory cycle.

See Synchronization Retrospective and Gating.

(PSIF) A heavily T2* weighted contrast enhanced gradient echo (mirrored FISP) technique. Because TE is relatively long, there are much flow artifacts and less signal to noise. In normal gradient echo techniques a FID-signal results after the RF pulses. This FID is rephased very fast and just before the next FID follows a spin echo signal. The SE is spoiled in FLASH sequences, but with PSIF sequences, only the SE is measured, not the FID.