(PARACEST) The alteration of the proton density or total water signal changes contrast and can be detected by the MRI scanner. Paramagnetic chemical exchange saturation transfer contrast agents are based upon the magnetization transfer mechanism.
Lanthanide ion complexes formed with tetra-amide based ligands display unusually slow water exchange kinetics and this feature may be used to alter image contrast by applying a selective presaturation pulse in an imaging sequence. This results in chemical exchange saturation transfer (CEST) from the lanthanide-bound water to bulk water thereby altering image contrast.
Chemical Exchange Saturation Transfer (CEST) agents are a class of contrast agents that could potentially revolutionize the MRI field because of their improved sensitivity and can have a great impact on functional magnetic resonance imaging.

Primovist™ (U.S brand name Eovist®) is a highly 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.
Primovist™ brightens the signal of T1 weighted MR images immediately after contrast administration. Dynamic scanning and imaging of the accumulation phase (best after 20 min.) can also be performed after bolus injection of Primovistâ„¢. The hepatocytes uptake will increase the signal intensity of normal liver parenchyma. 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.

ProHance® consists of a nonionic gadolinium complex (Gadoteridol) used as a paramagnetic MR contrast agent.
ProHance® provides contrast enhancement of the brain, spine and surrounding tissues resulting in improved visualization (compared with unenhanced MRI) of lesions with abnormal vascularity or those thought to cause a disruption of the normal blood brain barrier. ProHance® can also be used for whole body contrast enhanced MRI including the head, neck, liver, breast, musculoskeletal system and soft tissue pathologies.

WARNING: NEPHROGENIC SYSTEMIC FIBROSIS 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 Gadoteridol.

Vasovistâ„¢ is an albumin-targeted intravascular contrast agent. It is indicated for contrast enhanced MR angiography (CE-MRA) for the visualization of abdominal or limb vessels in patients with suspected or known vascular disease. After IV injection, Vasovistâ„¢ binds reversibly to human albumin in plasma, which results in long-lasting increased relaxivity. Imaging from 5 to 50 min is possible. A small unbound portion is, by glomerular filtration, eliminated by the kidneys.
AngioMARK® was the formerly trade name and MS-325 the research name. Currently the phase III clinical trials are completed to determine its efficacy for peripheral vascular disease and coronary artery disease.
In the U.S., EPIX received an approvable letter from the U.S. Food and Drug Administration (FDA) for Vasovistâ„¢ in January 2005. In 2009, Epix Pharmaceuticals has sold the U.S., Canadian and Australian rights for its blood pool agent (now named ABLAVARâ„¢), to Lantheus Medical Imaging, Inc..

WARNING: NEPHROGENIC SYSTEMIC FIBROSIS 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 the liver transplantation period.

See also MRI Safety.

ABLAVAR™ (formerly named Vasovistâ„¢) is a blood pool agent for magnetic resonance angiography (MRA), which opens new medical imaging possibilities in the evaluation of aortoiliac occlusive disease (AIOD) in patients with suspected peripheral vascular disease.
ABLAVARâ„¢ binds reversibly to blood albumin, providing imaging with high spatial resolution up to 1 hour after injection, due to its high relaxivity and to the long lasting increased signal intensity of blood.
As with other contrast media: the possibility of serious or life-threatening anaphylactic or anaphylactoid reactions, including cardiovascular, respiratory and/or cutaneous manifestations, should always be considered.

WARNING:
NEPHROGENIC SYSTEMIC FIBROSIS 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 Cardiovascular Imaging, Adverse Reaction, Molecular Imaging, and MRI Safety.