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Superparamagnetic Contrast AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Small particles of ferrite are used as superparamagnetic contrast medium in MR imaging (appearing predominantly dark on MRI). These agents exhibit strong T1 relaxation properties, and due to susceptibility differences to their surroundings also produce a strongly varying local magnetic field, which enhances T2 relaxation to darken the contrast media containing structures.
Superparamagnetic contrast agents are also known by the abbreviation SPIO's (small particle iron oxide or superparamagnetic iron oxide) and USPIO's (ultrasmall particle iron oxide or ultrasmall superparamagnetic iron oxide).
Two types of USPIO will be available on the market as blood pool agents, while SPIO's have been used as darkening contrast agents for liver imaging. As particulate matter they are taken up by the RES. Very small particles of less than 300 nanometers also remain intravascular for a prolonged period of time and thus can serve as blood pool agents.

See also the related poll result: 'The development of contrast agents in MRI is'
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• View the DATABASE results for 'Superparamagnetic Contrast Agents' (12).Open this link in a new window

 
Further Reading:
  News & More:
Optimized Labelling of Human Monocytes with Iron Oxide MR Contrast Agents
Sunday, 30 November 2003   by rsna2003.rsna.org    
Poly (dopamine) coated superparamagnetic iron oxide nanocluster for noninvasive labeling, tracking, and targeted delivery of adipose tissue-derived stem cells
Tuesday, 5 January 2016   by www.nature.com    
Superparamagnetic Iron OxideInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.
 
(SPIO) Relatively new types of MRI contrast agents are superparamagnetic iron oxide-based colloids (median diameter greater than 50nm). These compounds consist of nonstoichiometric microcrystalline magnetite cores, which are coated with dextrans (in ferumoxide) or siloxanes (in ferumoxsil). After injection they accumulate in the reticuloendothelial system (RES) of the liver (Kupffer cells) and the spleen. At low doses circulating iron decreases the T1 time of blood, at higher doses predominates the T2* effect.
SPIO agents are much more effective in MR relaxation than paramagnetic agents. Since hepatic tumors either do not contain RES cells or their activity is reduced, the contrast between liver and lesion is improved. Superparamagnetic iron oxides cause noticeable shorter T2 relaxation times with signal loss in the targeted tissue (e.g., liver and spleen) with all standard pulse sequences. Magnetite, a mixture of FeO and Fe2O3, is one of the used iron oxides. FeO can be replaced by Fe3O4.
Use of these colloids as tissue specific contrast agents is now a well-established area of pharmaceutical development. Feridex®, Endorem™, GastroMARK®, Lumirem®, Sinerem®, Resovist® and more patents pending tell us that the last word in this area is not said.
Some remarkable points using SPIO:
•
A minimum delay of about 10 min. between injection (or infusion) and MR imaging, extends the examination time.
•
Cross-section flow void in narrow blood vessels may impede the differentiation from small liver lesions.
•
Aortic pulsation artifacts become more pronounced.


See also Superparamagnetism, Superparamagnetic Contrast Agents and Classifications, Characteristics, etc..
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• View the NEWS results for 'Superparamagnetic Iron Oxide' (3).Open this link in a new window.

• View the DATABASE results for 'Superparamagnetic Iron Oxide' (32).Open this link in a new window

 
Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
  News & More:
How to stop using gadolinium chelates for magnetic resonance imaging: clinical-translational experiences with ferumoxytol
Saturday, 5 February 2022   by www.ncbi.nlm.nih.gov    
Polysaccharide-Core Contrast Agent as Gadolinium Alternative for Vascular MR
Monday, 8 March 2021   by www.diagnosticimaging.com    
Poly (dopamine) coated superparamagnetic iron oxide nanocluster for noninvasive labeling, tracking, and targeted delivery of adipose tissue-derived stem cells
Tuesday, 5 January 2016   by www.nature.com    
Longitudinal MRI contrast enhanced monitoring of early tumour development with manganese chloride (MnCl2) and superparamagnetic iron oxide nanoparticles (SPIOs) in a CT1258 based in vivo model of prostate cancer
Wednesday, 11 July 2012   by www.biomedcentral.com    
MRI Resources 
Open Directory Project - Safety pool - Education pool - Implant and Prosthesis - Stimulator pool - Abdominal Imaging
 
Superparamagnetism
 
Superparamagnetism occurs when the material is composed of very small crystallites (1-10 nm). In this case, even though the temperature is below the Curie or Néel temperature and the thermal energy is not sufficient to overcome the coupling forces between neighboring atoms, the thermal energy is sufficient to change the direction of magnetization of the entire crystallite. The resulting fluctuations in the direction of magnetization cause the magnetic field to average to zero. The material behaves in a manner similar to paramagnetism, except that instead of each individual atom being independently influenced by an external magnetic field, the magnetic moment of the entire crystallite tends to align with the magnetic field.
In MRI superparamagnetic iron oxide is used as a contrast agent.

See also magnetism, ferromagnetism, paramagnetism, and diamagnetism.
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• View the DATABASE results for 'Superparamagnetism' (6).Open this link in a new window

 
Further Reading:
  Basics:
Superparamagnetism
   by en.wikipedia.org    
  News & More:
Imagion (ASX:IBX) share price up 1,166% in a year pursuing adiation-freeâ„¢ cancer tech
Monday, 29 March 2021   by www.fool.com.au    
SuppressionForum -
there are related threads
 
One of a number of techniques designed to minimize the contribution of a particular component of the object to the detected signal. For example, commonly used to suppress the strong signal from water in order to detect spectral line from other components.

See also Fat Suppression and Water Suppression.
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• View the DATABASE results for 'Suppression' (49).Open this link in a new window

Supravistâ„¢InfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Short name: SHU 555 C, preliminary trade name: Supravistâ„¢
An ultrasmall superparamagnetic iron oxide under development as a positive enhancing blood pool agent (MRI contrast agent phase III, Bayer Schering Pharma AG). Supravist™ can be administered as an iv. bolus up to doses of 80 μmol/kg.

See also Ultrasmall Superparamagnetic Iron Oxide and Blood Pool Agents.
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• View the DATABASE results for 'Supravist™' (3).Open this link in a new window

MRI Resources 
Functional MRI - Implant and Prosthesis - Homepages - Artifacts - Devices - IR
 
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