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| frequency equal to the frequency of the photon which would cause a transition between the two energy levels of the spin. (x,y) |
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| T1 is the time to reduce the difference between the longitudinal magnetization (MZ) and its equilibrium value by a factor of e |
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| T2 is always less than or equal to T1. The net magnetization in the XY plane goes to zero and then the longitudinal magnetization grows in until we have Mo along Z. |
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T1-weighting causes fiber tracts (nerve connections, i.e. white matter) to appear white,
congregations of neurons (i.e. gray matter) to appear gray andcerebrospinal fluidtoappeardarkgray, and cerebrospinal fluidto appear dark. |
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| In a T2-weighted image, the contrast of "white matter," g g"gray matter'" and "cerebrospinal fluid" is reversed |
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Chelation is the formPFCation or presence of two or more separate bindings between a polydentate ligand and a single central atom. [1] Usually these ligands are organic compounds, and are called chelants, chelators, chelating agents, or sequestering agents.
The ligand forms a chelate complex with the substrate. Chelate complexes are contrasted with coordination complexes with monodentate ligands, which form only one bond with the central atom.
Chelants, according to ASTM-A-380, are "chemicals that form soluble, complex molecules with certain metal ions, inactivating the ions so that they cannot normally react with other elements or ions to produce precipitates or scale." |
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This water molecule interact/exchange with the gadolinium chelateWithout this interaction Gd-DTPA cannot create an MRI contrast
A completely chelated Gd is useless as an MRI contrast agent
Less chelation is better for contrast, but no for toxicity |
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| Why Iron Oxide Nanoparticles? |
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They are superparamagnetic
They are not magnetic until they are in the presence of an external magnetic field (external magnet)
The induced nanoparticle magnetic field affects the NMR/MRI signal of neighboring water molecules
H20.
They are biodegradable and non-toxic |
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| Absorption Coefficient of Light in Tissue |
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| Decreases with wavelength. (purple=most, red=least) |
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| Gold chemical and catalytic properties |
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| Gold nanospheres/nanorods have a high affinity for thiol containing molecules and polymers |
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| Iron Oxide chemical and catalytic properties |
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Iron oxide nanospheres/nanorods have a high affinity for carboxylated molecules and polymers
Iron oxide nanospheres/nanorods also bind molecules containg hydroxyl groups and hydroxylated polymers. |
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One can entrap molecules (dyes, drugs) within polymeric cavities.
Caution! (fluorophore quenching) |
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X-rayCTusesionizingX-rayradiationXray CT uses ionizing Xray radiation and it is good for dense tissues (bone, coins and nails)
MRI uses radiofrequency signals and a magnetic field and it is good for soft, non-calcified tissues (muscle, cartilages, and Kiwi) |
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PFC-is a perfluorocarbon which is FDA approved and known to be non-toxic. It is known to be
exhale through the lungs. These “nanobubbles” are approximately 100 nm is size and are long circulating |
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| Size of polymer coating is important |
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| Nanoparticles coated with the 500Kdextrangivesthebest500 K dextran gives the best |
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