(I) Property of all nuclei related to the largest measurable component of the nuclear angular momentum. Non-zero values of nuclear angular momentum are quantized (fixed) as integral or half-integral multiples of (h/2p), where h is Planck's constant. The number of possible energy levels for a given nucleus in a fixed magnetic field is equal to 2I + 1. Similarly, an unpaired electron has a spin of 1/2 and two possible energy levels.

(USPIO) The class of the ultrasmall superparamagnetic iron oxide includes several chemically and pharmacologically very distinct materials, which may or may not be interchangeable for a specific use. Some ultrasmall SPIO particles (median diameter less than 50nm) are used as MRI contrast agents (Sinerem®, Combidex®), e.g. to differentiate metastatic from inflammatory lymph nodes. USPIO shows also potential for providing important information about angiogenesis in cancer tumors and could possibly complement MRI helping physicians to identify dangerous arteriosclerosis plaques.
Because of the disadvantageous large T2*//T1 ratio, USPIO compounds are less suitable for arterial bolus contrast enhanced magnetic resonance angiography than gadolinium complexes. The tiny ultrasmall superparamagnetic iron oxides do not accumulate in the RES system as fast as larger particles, which results in a long plasma half-life. USPIO particles, with a small median diameter (less than 10 nm), will accumulate in lymph nodes after an intravenous injection by e.g. direct transcapillary passage through endothelial venules. Once within the nodal parenchyma, phagocytic cells of the mononuclear phagocyte system take up the particles.
As a second way, USPIOs are subsequently taken up from then interstitium by lymphatic vessels and transported to regional lymph nodes. A lymph node with normal phagocytic function takes up a considerable amount and shows a reduction of the signal intensity caused by T2 shortening effects and magnetic susceptibility. Caused by the small uptake of the USPIOs in metastatic lymph nodes, they appear with less signal reduction, and permit the differentiation of healthy lymph nodes from normal-sized, metastatic nodes.

See also Superparamagnetic Contrast Agents, Superparamagnetic Iron Oxide, Very Small Superparamagnetic Iron Oxide Particles, Blood Pool Agents, Intracellular Contrast Agents.

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.

(VSOP) A new class of contrast agents with smaller particle size than SPIO or USPIO with advantages for MR angiography, caused through a longer plasma half-life.

See also Ultrasmall Superparamagnetic Iron Oxide and Superparamagnetic Iron Oxide.