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MRI Contrast Agents
• Classifications, Characteristics, etc. •
• Contrast Agents For Intravenous Use / Magnetic Characteristics
• Contrast Agents For Intravenous Use / Pharmacokinetics
• Contrast Agents For Intravenous Use / Distribution
• Contrast Agents For Oral Use / Magnetic Characteristics
• Contrast Agents For Oral Use / Signal Characteristics
  
Radiology Contrast Agents Open this link in a new window Ultrasound Imaging Contrast Agents Open this link in a new window
Contrast Agents For Intravenous Use / Distribution
Blood Pool Agents 
Blood pool agents (intravascular contrast agents) remain in the blood for a prolonged time compared with conventional contrast agents, which diffuse quickly into the interstitial space. Magnetic resonance angiography (MRA), cardiovascular imaging, or contrast enhanced MRIs are possible over an hour or more. This advantage over conventional MRI contrast media allows also higher resolution MRA of several territories using respiratory or cardiac gating techniques with a single contrast bolus.
Different types of blood pool contrast agents:
Ultrasmall superparamagnetic iron oxide (USPIO)
Gd Labeled Albumin
Chromium labeled red blood cells
Gd-DTPA labeled dextran
Blood pool MRI contrast agents with their longer intravascular circulation can be designed to be targeted to necrotic myocardium, to assess myocardial viability, or tumor directed to provide better diagnostic information for various tumors. A disadvantage of the use of blood pool agents for MRA is that the separation of arteries and veins is more difficult because they are present in both and the overlapping of those vessels is disturbing. This can be solved by e.g. different MIP segmentation algorithms.
See also Necrosis Avid Contrast Agent, Tumor Specific Agents, Feruglose, Gadofosveset Trisodium (Vasovist), Ultrasmall Superparamagnetic Iron Oxide and Contrast Medium.


• View the NEWS results for 'Blood Pool Agents' (1).Open this link in a new window.

• View the DATABASE results for 'Blood Pool Agents' (16).Open this link in a new window

 
Further Reading:
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 analyze and evaluate the liver function (in cases of diffuse liver diseases e.g., cirrhosis).
Imaging of the gallbladder and biliary system 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.
See also Superparamagnetic Contrast Agents, Hepatobiliary Chelates, Liver Imaging, Endorem™, Primovist™, and Classifications, Characteristics, etc.

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

• View the DATABASE results for 'Hepatobiliary Contrast Agents' (11).Open this link in a new window

 
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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)

• View the DATABASE results for 'Intracellular Contrast Agents' (3).Open this link in a new window

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.

• View the DATABASE results for 'Reticuloendothelial Contrast Agents' (3).Open this link in a new window

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  Contrast Agents For Oral Use / Magnetic Characteristics top
Radiology Contrast Agents Open this link in a new window Ultrasound Imaging Contrast Agents Open this link in a new window
 
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