Magnetic Resonance TIP - MRI Database : Contrast Agents

Magnetic Resonance - Technology Information Portal

Friday, 20 November 2009

••

Database

Forum

Market

News

Protocols

Contact

Info
Sheets

Artifacts

Coils

Contrast Agents

Devices

Images

Sliders

Sequences

Abbreviations

Acronyms

Patient
Information

Out-
side

Congresses

	Resources

See a comprehensive list of contrast agents!
From Abdoscan® to Teslascan®.

'Contrast Agents'

Result : Searchterm 'Contrast Agents' found in 17 terms [

] and 95 definitions [

]

1 - 5 (of 112) nextResult Pages :

[1 2 3 4]

[5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ... ]

bottom

Searchterm 'Contrast Agents' was also found in the following services of MR-TIP.com:

News (32)

Resources (12)

Forum (8)

Contrast Agents

Contrast agents are chemical substances introduced to the anatomical or functional region being imaged, to increase the differences between different tissues or between normal and abnormal tissue, by altering the relaxation times. MRI contrast agents are classified by the different changes in relaxation times after their injection.

	Positive contrast agents cause a reduction in the T1 relaxation time (increased signal intensity on T1 weighted images). They (appearing bright on MRI) are typically small molecular weight compounds containing as their active element Gadolinium, Manganese, or Iron. All of these elements have unpaired electron spins in their outer shells and long relaxivities. Some typical contrast agents as gadopentetate dimeglumine, gadoteridol, and gadoterate meglumine are utilized for the central nervous system and the complete body; mangafodipir trisodium is specially used for lesions of the liver and gadodiamide for the central nervous system.
	Negative contrast agents (appearing predominantly dark on MRI) are small particulate aggregates often termed superparamagnetic iron oxide (SPIO). These agents produce predominantly spin spin relaxation effects (local field inhomogeneities), which results in shorter T1 and T2 relaxation times. SPIO's and ultrasmall superparamagnetic iron oxides (USPIO) usually consist of a crystalline iron oxide core containing thousands of iron atoms and a shell of polymer, dextran, polyethyleneglycol, and produce very high T2 relaxivities. USPIOs smaller than 300 nm cause a substantial T1 relaxation. T2 weighted effects are predominant.
	A special group of negative contrast agents (appearing dark on MRI) are perfluorocarbons (perfluorochemicals), because their presence excludes the hydrogen atoms responsible for the signal in MR imaging.

The design objectives for the next generation of MR contrast agents will likely focus on prolonging intravascular retention, improving tissue targeting, and accessing new contrast mechanisms. Macromolecular paramagnetic contrast agents are being tested worldwide. Preclinical data shows that these agents demonstrate great promise for improving the quality of MR angiography, and in quantificating capillary permeability and myocardial perfusion.
Ultrasmall superparamagnetic iron oxide (USPIO) particles have been evaluated in multicenter clinical trials for lymph node MR imaging and MR angiography, with the clinical impact under discussion. In addition, a wide variety of vector and carrier molecules, including antibodies, peptides, proteins, polysaccharides, liposomes, and cells have been developed to deliver magnetic labels to specific sites. Technical advances in MR imaging will further increase the efficacy and necessity of tissue-specific MRI contrast agents.

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

Images, Movies, Sliders:

Delayed Myocardial Contrast Enhancement from Infarct

Courtesy of Robert R. Edelman

Left Circumflex Ischemia First-pass Contrast Enhancement

MR Colonography Gadolinium per Rectum

Courtesy of Robert R. Edelman

CE MRA of the Aorta

Slider

Further Reading:

Basics:

	MRI Contrast Agent(.pdf) 2000 by jbfpc2.ycp.edu

	Contrast Agents in Magnetic Resonance Imaging 1997

	Early Distribution Dynamics of Polymeric Magnetic Resonance Imaging Contrast Agents in Rats1, page 412(.pdf) 2002 by www.academicradiology.com [Free, but registration is required.]

News & More:

	Chembytes e-zine, Special agents 1998

	Drastic market changes with MRI contrast media and PET radiopharmaceuticals emerging as most promising segments Thursday, 21 October 2004 by www.news-medical.net

•• There are 25 news about 'Contrast Agents'.

MRI Resources

Pregnancy - Mobile MRI Rental - Examinations - Diffusion Weighted Imaging - Non-English - Homepages

Oral Contrast Agents

A limitation of abdominal MRI can be the assessment of malignancies by difficulties to distinguish bowel from other organs or malignant masses. The use of oral contrast agents can reduce this problem. Properties of an ideal oral contrast agent are little or no absorption by the stomach or intestines, complete excretion, no motion or susceptibility artifacts, and uniform marking of the GI tract.
Gastrointestinal MRI contrast agents are divided in materials with bright appearance or dark appearance. The choice of a negative or a positive oral contrast agent depends on the specific problem or the pulse sequence.
See also Positive Oral Contrast Agents, Negative Oral Contrast Agents, Gastrointestinal Diamagnetic Contrast Agents, Gastrointestinal Paramagnetic Contrast Agents and Gastrointestinal Superparamagnetic Contrast Agents.

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

Further Reading:

News & More:

Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CT

2000

Searchterm 'Contrast Agents' was also found in the following services of MR-TIP.com:

News (32)

Resources (12)

Forum (8)

Paramagnetic Contrast Agents

Magnetic relaxation in tissues can be enhanced using contrast agents. The most commonly used for MRI are the paramagnetic contrast agents, which have their strongest effect on the T1, by increasing T1 signal intensity in tissues where they have accumulated.
MRI collects signal from the water protons, but the presence of these contrast agents enhances the relaxation of water protons in their vicinity. Paramagnetic contrast agents contain magnetic centers that create magnetic fields approximately one thousand times stronger than those corresponding to water protons. These magnetic centers interact with water protons in exactly the same way as the neighboring protons, but with much stronger magnetic fields, and therefore, have a much greater impact on relaxation rates, particularly on T1. In MRI, contrast agents are routinely injected intravenously to help identify areas of hypervascularity, as in malignant tumors.
See also Contrast Agents, Gadovist®, MultiHance®, Omniscan®, OptiMARK®.

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

Images, Movies, Sliders:

MRI Upper Abdomen T1 with Contrast

MRI Orbita T1

MRI Orbita T1 with Contrast

Further Reading:

Basics:

LEARNING CENTER FOR PARAMAGNETISM

2003 by www.naturesalternatives.com

News & More:

	MRI Contrast Agent(.pdf) 2000 by jbfpc2.ycp.edu

	Contrast Agents in Magnetic Resonance Imaging 1997

	Gadolinium(.pdf) 2000

	A Virtual International Relaxometry Laboratory

•• There is 1 news about 'Paramagnetic Contrast Agents'.

MRI Resources

Diffusion Weighted Imaging - Mobile MRI - Safety pool - Portals - Safety Products - Collections

Ferromagnetic Contrast Agents

A contrast agent, which due to their ferromagnetism produce local field inhomogeneities and hence visible image alterations in the tissues where they are present. Therefore, they can act as contrast media. Usually, particles exhibiting superparamagnetism rather than ferromagnetism are used.

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

Searchterm 'Contrast Agents' was also found in the following services of MR-TIP.com:

News (32)

Resources (12)

Forum (8)

Hepatobiliary Contrast Agents

The characteristics of a hepatobiliary contrast agent are specific liver uptake and excretion via the biliary system. The paramagnetic substance (e.g. manganese, gadolinium) is taken up by normal hepatocytes. Diseased liver tissue did not include hepatocytes or their function is disturbed. Therefore, the signal of healthy liver tissue increases on T1 weighted sequences, but not in the liver lesions.
Another type of liver imaging contrast agent is superparamagnetic iron oxide. These particles accumulate in the reticuloendothelial system (RES) of the liver, and darken the healthy liver tissue in T2 weighted images. RES cells (including Kupffer cells) are existing in healthy liver tissue, in altered tissue with reduced RES activity or without RES cells the contrast agent concentration is also low or not existing, which improves the liver to lesion contrast.
Benefits of hepatobiliary contrast agents:

	Liver lesions (e.g., tumor, metastases, haemangioma etc.) are better detectable and to characterize.
	These contrast agents are useful to analyse and evaluate the liver function (in cases of diffuse liver diseases e.g., cirrhosis).
	Imaging of the gallbladder and biliary sytem is improved.

Differences of a hepatobiliary contrast agent compared with a targeted contrast agent for Kupffer cells:

	The higher number of hepatocytes than Kupffer cells improves the uptake effectiveness of the contrast agent.
	Hepatobiliary contrast agents enable a better opacification of the biliary ducts and the gallbladder caused by the biliary excretion.
	Hepatobiliary contrast media are fast excreted agents. RES targeted contrast agents remain longer in the body, a fact that can increase possible side effects.

Further Reading:

Basics:

LIVER-SPECIFIC CONTRAST AGENTS FOR MRI

(.pdf)

News & More:

	MAGNETIC RESONANCE IMAGING OF FOCAL LIVER LESIONS(.pdf) 2002

	Researchers are learning to make designer cells for dehydrated blood supplies and space-age medicines. Saturday, 16 July 2005 by www.firstscience.com