(LE) Myocardial late enhancement in contrast enhanced cardiac MRI has the ability to precisely delineate myocardial scar associated with coronary artery disease. Viability imaging implies evaluating infarcted myocardium to see whether there is enough viable tissue available for revascularization. The reversal of myocardial dysfunction is particularly relevant in patients with depressed ventricular function because revascularization improves long-term survival. In comparison to SPECT and PET imaging, myocardial late enhancement MRI demonstrates areas of delayed enhancement exactly in correlation with the infarcted region.
Viability on cardiac MRI (CMR) is based on the fact that all infarcts enhance vividly 10-15 minutes after the administration of intravenous paramagnetic contrast agents. This enhancement represents the accumulation of gadolinium in the extracellular space, due to the loss of membrane integrity in the infarcted tissue. This phenomenon of delayed hyperenhancement has been proven to correlate with the actual extent of the infarct.
MRI myocardial late enhancement can quantify the size, location and transmural extent of the infarct. If the transmural extent of the infarct (region of enhancement on MRI) is less than 50% of the wall thickness, there will be improved contractility in that segment following revascularization. In areas of hypokinesia, if there is a rim of "black" or non-infarcted myocardium that is not contracting well, it indicates the presence of hibernating myocardium, which is likely to improve after revascularization of the artery supplying that particular territory.
The total duration of a myocardial late enhancement MR imaging protocol for viability is approximately 30 minutes, including scout images, first-pass images, cine images in two planes, and delayed myocardial enhancement images. In order to assess viable myocardium, the gadolinium contrast agent is injected at a dose of 0.15 to 0.2 mmol/kg. After about 10 minutes, short axis and long axis views (see cardiac axes) of the heart are obtained using an inversion prepared ECG gated gradient echo sequence. The inversion pulse is adjusted to suppress normal myocardium. Areas of nonviable myocardium retain extremely high signal intensity, black areas show normal tissue.

For Ultrasound Imaging (USI) see Myocardial Contrast Echocardiography at Medical-Ultrasound-Imaging.com.

Short name: NC100150, PEG-feron, generic name: Feruglose, preliminary trade name: Clariscan™
NC100150 injection is the code name for an USPIO (ultrasmall superparamagnetic iron oxide) MRI contrast agent under development. Microvessel permeability depends on functional and morphologic characteristics of cancer vessels and on physicochemical properties of the injected contrast medium molecule.
USPIO particles have a favorable pharmacological and tolerance profile and are being tested clinically of the potential for the quantitative characterization of tumor microvasculature and specifically for measures of the microvessel permeability. Iron-based products take advantage of their large molecular size, which prevents diffusion into body tissues. These agents are disposed of by the liver and spleen as particulate matter.
NC100150 Injection (Nycomed Amersham, Amersham Health ) consists of USPIO particles that are composed of single crystals (4- to 7-nm diameter) and stabilized with a carbohydrate polyethylene glycol (PEG) coat. The iron oxide particles have to be suspended in an isotonic glucose solution. The final diameter of an USPIO particle is approximately 20 nm. Blood pool half-life is more than two hours in humans; the particles are taken up by the mononuclear phagocyte system and distributed mainly to the liver and spleen.
NC100150 would compete with the contrast agents Ferumoxytol from AMAG Pharmaceuticals, Inc. and Vasovist™ from EPIX Pharmaceuticals, Inc., but at this time the development of NC100150 Injection/Clariscan™ is discontinued.

(NACA) Some porphyrin (e.g. Gadophrin-2) and non-porphyrin (e.g. CEIII-60) paramagnetic chelates are able to specifically accumulate in nonviable tissues and can be applied as a MRI contrast agent for acute myocardial infarction and therapeutic necrosis. This function of necrosis avid contrast agents is a unique pathological targetability. These agents can also be exploited for multipurpose applications, because NACAs also bear other common properties including early systemic distribution, albumin binding, hepatocellular uptake and renal elimination.

See also the related poll result: 'The development of contrast agents in MRI is'

Omniscan® is a nonionic chelate complex with low osmolality used as a paramagnetic MRI contrast agent. The efficacy of Omniscan® is similar to that of Gd-DTPA. Omniscan® is given intravenously to enhance images of intracranial and spinal lesions where there is abnormal vascularity or an abnormal blood brain barrier. The complex does not cross an intact blood brain barrier so Omniscan® only accumulates in lesions such as neoplasm's and abscesses.

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 Gadodiamide, and Classifications, Characteristics, etc.

The activation of the brain is mirrored in the local changes in metabolism and hemodynamics (brit. haemodynamics). By using heavily T2 weighted scans activated brain areas show an increase in signal intensity as oxyhaemoglobin (brit. oxyhaemoglobin) is diamagnetic and deoxyhemoglobin (brit. deoxyhaemoglobin) is paramagnetic. Oxygen mapping will benefit from high field strength.

See also Blood Oxygenation Level Dependent Contrast, Haemoglobin, Perfusion Imaging, Diamagnetism, Paramagnetism.