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Most clinically used MRI contrast agents work by shortening the T1 relaxation time of protons inside tissues via interactions with the nearby contrast agent. Thermally driven motion of the strongly paramagnetic metal ions in the contrast agent generate the oscillating magnetic fields that provide the relaxation mechanisms that enhance the rate ...
A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. [1] Contrast agents absorb or alter external electromagnetism or ultrasound , which is different from radiopharmaceuticals , which emit radiation themselves.
Extracellular contrast agents are used widely in liver MRI, and newer hepatobiliary contrast agents also provide the opportunity to perform functional biliary imaging. Anatomical imaging of the bile ducts is achieved by using a heavily T2-weighted sequence in magnetic resonance cholangiopancreatography (MRCP).
However, most contrast agents used in MRI are selected for their specific magnetic properties. Most commonly, a paramagnetic contrast agent (usually a gadolinium compound [7] [8]) is given. Gadolinium-enhanced tissues and fluids appear extremely bright on T 1-weighted images. This provides high sensitivity for detection of vascular tissues (e.g ...
The contrast agents absorb external X-rays, resulting in decreased exposure on the X-ray detector. This is different from radiopharmaceuticals used in nuclear medicine which emit radiation. Magnetic resonance imaging (MRI) functions through different principles and thus MRI contrast agents have a different mode of action. These compounds work ...
Commonly, peptides, antibodies, or small ligands, and small protein domains, such as HER-2 affibodies, have been applied to achieve targeting. To enhance the sensitivity of the contrast agents, these targeting moieties are usually linked to high payload MRI contrast agents or MRI contrast agents with high relaxivities. [2]
In the sole paper describing in vivo use of enzyme-activated MR contrast agents, the agent was delivered to embryonic cells via a micropipette. However, the authors of the paper acknowledge that this is not a feasible approach for many research projects, [ 5 ] and it presents a clear impediment to clinical use.
Iodinated contrast is a form of water-soluble, intravenous radiocontrast agent containing iodine, which enhances the visibility of vascular structures and organs during radiographic procedures. Some pathologies, such as cancer , have particularly improved visibility with iodinated contrast.