Magnetic Resonance TIP - MRI Database : Liposomes

Magnetic Resonance - Technology Information Portal

Tuesday, 9 February 2010

••

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®.

'Liposomes'

Result : Searchterm 'Liposomes' found in 1 term [

] and 4 definitions [

]

1 - 5 (of 5) Result Pages :

[1]

bottom

Searchterm 'Liposomes' was also found in the following service of MR-TIP.com:

News (2)

Liposomes

Generic name: Liposomes, central moiety: different, contrast effect: paramagnetic, distribution: different
Liposomes are lipid containing nanoparticles, or fat molecules, surrounding a water core. Liposomes were the first type of nanoparticles created to be used as carriers for lipophilic MRI contrast agents with novel characteristics.
Liposomes loaded with gadolinium-containing chelates have potential as blood pool agents, caused by modifications of the surface (e.g., with polyethylene glycol) leading to longer blood retention times.
The incorporation of contrast agents into either the the bilayer membrane or the aqueous inner cavity is possible. These MRI contrast agents has been used to image the lymph nodes using liposomes containing Gd-DTPA as well as dextran coated iron oxide particles.
To image the liver or the hepatobiliary system, liposomes containing Gd-HPDO3A, or MnDPDP, have been tested.
Liposomes containing gadolinium were conjugated to antibodies and targeted to a specific organ system.
A method of targeting tumors with ultrasound that also uses MRI to watch the cell destroying, uses liposomes loaded with cytotoxic drugs and also with gadolinium to make them show up in MRI. As well as used as an imaging technique, ultrasound can also be used to destroy cancer cells. Once the drugs have been administered, focusing the ultrasound on the target area makes blood vessels permeable. The liposomes leak out of the blood vessel into the target area, watched by MRI, where the cytotoxic drug can then go to work.
See also Memosomes, Superparamagnetic Iron Oxide, Classifications, Characteristics, etc. and Mangafodipir Trisodium.

Further Reading:

Basics:

	Novel Agent for Lymph Node Imaging and Targeted Gene Therapy 1997

	DELIVERY AND ACTIVATION OF CONTRAST AGENTS FOR MAGNETIC RESONANCE IMAGING(.pdf) by etd.caltech.edu

	The Laboratory of Liposome Research by www.unizh.ch

News & More:

	Molecular Magnetic Resonance Imaging(.pdf) 2005 by www.medical.siemens.com

	Gd-Labeled Liposomes for Monitoring Liposome-encapsulated Chemotherapy: Quantification of Regional Uptake in Tumor and Effect on Drug Delivery(.pdf) July 2002 by www.academicradiology.com [Free, but registration is required.]

•• There is 1 news about 'Liposomes'.

MRI Resources

Absorption and Emission - Portals - Shielding - Examinations - Services and Supplies - Mass Spectrometry

Memosomes

Short name: Mn-EDTA-PP, generic name: Liposomes, central moiety: Mn2+, preclin. trade name: Memosomes
Memosomes are taken up by healthy Kupffer cells of the liver. Once in this cells, manganese (Mn+2) release slowly and diffuses into the adjoining hepatocytes. Normal liver tissue (not malignancies) is enhanced after application of this type of liposomes.
See also Liposomes, Hepatobiliary Contrast Agents, and Reticuloendothelial Contrast Agents.
See also Classifications, Characteristics, etc.

Further Reading:

News & More:

The Laboratory of Liposome Research

by www.unizh.ch

Searchterm 'Liposomes' was also found in the following service of MR-TIP.com:

News (2)

Intracellular Contrast Agents

Contrast agent with a preferential intracellular distribution.
Intracellular agents (such as manganese derivatives and ultrasmall superparamagnetic iron oxide), exhibit a flow- and metabolism-dependent uptake. These properties may allow delayed imaging, similar to isotopic methods.
Phospholipid liposomes are rapidly sequestered by the cells in the reticuloendothelial system (RES), primarily in the liver. For imaging of the liver, liposomes may be labeled with MR contrast medium, both positive (T1-shortening) paramagnetic media, and negative (T2-shortening) superparamagnetic media.
Several other nonliposome MR contrast media are also taken up by the RES, e.g.:

	superparamagnetic iron oxide (SPIO)
	ultrasmall superparamagnetic iron oxide (USPIO)
	monocrystalline iron oxide nanoparticle (MION)

Other MR contrast agents accumulate selectively in the hepatocytes, e.g.:

	gadoxetic acid (Gd-EOB-DTPA)
	gadobenate dimeglumine (Gd-BOPTA)
	mangafodipir trisodium (Mn-DPDP)

Further Reading:

Basics:

Degradation, Metabolism and Relaxation Properties of Iron Oxide

(.pdf)

2004 by www.diva-portal.org

News & More:

Three Types of Physical Measurements Neededto Characterize Iron OxideNanoparticles for MRI and MRA, Academic Radiology, Vol 9, Suppl 1

(.pdf)

2002 by www.academicradiology.com [Free, but registration is required.]

MRI Resources

Education pool - Databases - Portals - Colonography - MRI Technician and Technologist Career - Cardiovascular Imaging

Reticuloendothelial Contrast Agents

Liver imaging with gadolinium contrast enhanced MRI is sometimes not sufficient for a reliable diagnosis of liver lesions. For this reasons, special liver Contrast agents that are targeted to the reticuloendothelial system (RES), have been developed to improve both detection and characterization of liver and spleen lesions. Reticuloendothelial Contrast Agents, as e.g. superparamagnetic iron oxides (SPIO), are taken up by healthy liver tissue but not tumors.
These RES targeted contrast agents provide a prolonged imaging window and enough time for high spatial resolution or multiple breath hold images. Reticuloendothelial contrast agents have an increased sensitivity for the detection of small liver lesions (e.g., metastases), compared with gadolinium enhanced MRI and spiral CT. At higher field strengths with an increased signal to noise ratio the susceptibility effect with iron oxide particles may be enhanced.
Other new agents (Gadobenate Dimeglumine, Gadoxetic Acid) have both an initial extracellular circulation and a delayed liver-specific uptake. Since a considerable part of these contrast agents is excreted in the bile, functional biliary imaging can diagnose biliary anomalies, postoperative bile leaks, and anastomotic strictures. Other agents, such as liposomes (with encapsulated Gd-DTPA) or DOTA complexes are in different development stages.
See also Hepatobiliary Contrast Agents, Gadolinium Oxide, Superparamagnetic Iron Oxide and Liposomes.

Further Reading:

Basics:

MRI Contrast Agents: A Dynamic Field in Flux

by www.imagingeconomics.com

News & More:

Researchers are learning to make designer cells for dehydrated blood supplies and space-age medicines.

Saturday, 16 July 2005 by www.firstscience.com

Searchterm 'Liposomes' was also found in the following service of MR-TIP.com:

News (2)

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