OptiMARK® is a formulation of a nonionic gadolinium chelate of diethylenetriamine pentaacetic acid bismethoxyethylamide (gadoversetamide), for use as a paramagnetic MRI contrast agent. OptiMARK® (gadoversetamide injection) is to be administered by intravenous injection. OptiMARK® is indicated for MRI diagnostic procedures to provide increased enhancement and visualization of lesions of the brain, spine and liver, including tumors.

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.

(OMP) Various mixtures of gastrointestinal diamagnetic contrast agents for use as negative oral contrast agents to darken the bowel.

(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.

Paramagnetic materials attract and repel like normal magnets when subject to a magnetic field. This alignment of the atomic dipoles with the magnetic field tends to strengthen it, and is described by a relative magnetic permeability greater than unity. Paramagnetism requires that the atoms individually have permanent dipole moments even without an applied field, which typically implies a partially filled electron shell. In pure Paramagnetism (without an external magnetic field), these atomic dipoles do not interact with one another and are randomly oriented in the absence of an external field, resulting in zero net moment.
Paramagnetic materials in magnetic fields will act like magnets but when the field is removed, thermal motion will quickly disrupt the magnetic alignment. In general, paramagnetic effects are small (magnetic susceptibility of the order of 10^-3 to 10^-5).
In MRI, gadolinium (Gd) one of these paramagnetic materials is used as a contrast agent. Through interactions between the electron spins of the paramagnetic gadolinium and the water nuclei nearby, the relaxation rates (T1 and T2) of the water protons are increased (T1 and T2 times are decreased), causing an increase in signal on T1 weighted images.

See also contrast agents, magnetism, ferromagnetism, superparamagnetism, and diamagnetism.

Pharmacyclics is a pharmaceutical company developing novel agents to improve current therapeutic approaches to cancer, cardiovascular diseases, and inflammation. The company's proprietary products are derived from its core technology in biometallic chemistry. These products under development are based upon small molecules, which bind metals in a unique way and are capable of capturing and focusing forms of energy used in a variety of medical applications. The company has one product in registration with the FDA, Gadolite® Oral Suspension, a contrast agent for imaging the gastrointestinal tract; two products in clinical development, Gd-Tex (Motexafin gadolinium), a radiation sensitizer, Lu-Tex, a photosensitizer; and several compounds in preclinical development.

MRI Contrast Agents: