Ans: A (Gadolinium) 'The contrast dye used in these MRI Scans is generallygadalinturn as complications are rarer in comparison to the iodine origin dye used for x-rays and CT scans"- mriscans.diniccompare.co. uk/ mri-scan-with-contrast-dye"Technetium : Its short-lived gamma ray-emitting nuclear isomer--technetium-99m--is used in nuclear medicine for a wide variety of diagnostic tests. Technetium-99 is used as a gamma ray-free source of beta particles. Technetium-99m ("m" indicates that this is a metastable nuclear isomer) is used in radioactive isotope medical tests, for example as a radioactive tracer that medical equipment can detect in the human body"- en.wikipedia.org/wiki/Technetium"Indium is a chemical element. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows intermediate properties between these two. Indium's current primary application is to form transparent electrodes from indium tin oxide (1T0) in liquid crystal displays and touchscreens" en.wikipedia.org/wiki/ TechnetiumMR1 CONTRAST AGENTSMRI contrast agents are a group of contrast media used to improve the visibility of internal body structures in magnetic resonance imaging (MR!). The most commonly used compounds for contrast enhancement are gadolinium- basedMost clinically used MR! contrast agents work through shortening the T1 relaxation time ofprotons located nearbyMRI contrast agents may be administered by injection into the blood stream or orally, depending on the subject of interest. Oral administration is well suited to G.I. tract scans, while intravascular administration proves more useful for most other scans. A variety of agents of both types enhance scans routinely.MRI contrast agents can be classified in many ways including by their:1. chemical composition2. administration route3. magnetic properties4. effect on the image5. presence and nature of metal atoms6. biodistribution and applications:I Extracellular fluid agents (also known as intravenous contrast agents)II Blood pool agents (also known as in travascular con trast agents)III Organ specific agents (i.e. Gastrointestinal contrast agents and hepatobiliary contrast agents)IV Active targeting/cell iabeling agents (i.e. tumor-specific agents)V Responsive (also known as smart or bioactivated) agentsVI pH-sensitive agentsTypes of contrasts in MRI1. Gadolinium2. Iron oxide: Superparamagnetic: Two types of iron oxide contrast agents exist: superparamagnetic iron oxide (SP10) and ultrasmall superparamagnetic iron oxide (U3PIO) e.g includes Feridex I.V. Resovist, Sinerem, Lumirem & Clariscan3. Iron Platinum: Superparamagnetic: Superparamagnetic iron platinum particles (SIPPs) have been reported and had significantly better T2 relaxivities compared with the more common iron oxide nanoparticles. SIPP swere also encapsulated with phospholipids to create multifunctional SIPP stealth immunomicelles that specifically targeted uman prostate cancer cells.4. Manganese: Paramagnetic: Unlike the other well-studied iron oxide-based nanoparticles, research on Mn-based nanoparticles is at a relatively early stage. Manganese ions (Mn2+) are often used as a contrast agent in animal studies, usually referred to as MEMRI (Manganese Enhanced MRI).5. Oral administration of contrast agents:A wide variety of oral contrast agents can enhance images of the gastrointestinal tract. Perflubron, a type of perfluorocarbon, has been used as a gastrointestinal MR! contrast agent for pediatric imaging.6. Protein-based MRI contrast agents: Newer research suggests the possibility of protein based contrast agents, based on the abilities of some amino acids to bind with gadolinium. Heme-containing proteins may act as "natural" contrast agents, just like previously discussed iron(IH) porphyrinsGadolinium"Some patients undergoingan MRI scan may require an injection of an intravenous (IV) dye (contrast) known as Gadolinium, which is a paramagnetic substance that is visible on MRI scans. The contrast is delivered into your body through a small plastic tube known as an intravenous cannula, which is placed into a vein in your arm by a nurse or radiographer who are both experienced in performing this procedure. This will result in a minor discomfort, usually no more than taking blood from your arm. The IV contrast is NOT radioactive""Gadolinium chelates have been approved for parenteral use since the late 1980s. Although these agents can be differentiated on the basis of stability, viscosity, and osmolality, they cannot be differentiated on the basis of efficacy. Gadolinium chelates are extremely well tolerated by the vast majority of patients in whom they are injected. Acute adverse reactions are encountered with a lower frequency than is observed after administration of iodinated contrast media""Gadolinium-containing contrast agents approved for human use. Some are-gadoterate (Dotarem)gadodiamide (Omniscan), gadobenate (MultiHance), gadopentetate (Magnevist, Magnegita, Gado-MRT ratiopharmfgadoteridol (ProHancefgadoversetamide (OptiMARK), gadoxetate (Primovist) & gadobutrol (Gadovist)Radiocontrast agents used in Radiology# Radiocon trust agents are a type of medical contrast medium used to improve the visibility of internal bodily structures in X-ray based imaging techniques such as computed tomography (CT) and radiography (commonly known as X-ray imaging). Radiocontrast agents are typically iodine or barium compounds.# Magnetic resonance imaging (MR!) functions through different principles and thus utilizes different contrast agents. These compounds work by altering the magnetic properties of nearby hydrogen nuclei.# Iodine-based contrast media are usually classified as ionic or non-ionic Both types are used most commonly in radiology due to their relatively harmless interaction with the body and its solubility. Contrast media are primarily used to visualize vessels and changes in tissues on radiography and CT. There are many different molecules. Some examples of organic iodine molecules are iohexol, iodixanol and ioversol. Barium sulfate is mainly used in the imaging of the digestive system. The substance exists as a water insoluble white powder that is made into a slurry with water and administered directly into the gastrointestinal tract.# Barium sulfate, an insoluble white powder is typically used for enhancing contrast in the GI tract# An older type of contrast agent, Thorotrast was based on thorium dioxide, but this was abandoned since it turned out to be carcinogenic.