Transfer MRI

MT MRI has been showm to be sensitive to other minor structural abnormalities caused by neurological disease. MTR maps were analyzed with a statistical package demonstrated that areas of epileptic activity which were not detected visually had statistically reduced MTR in the epileptic focus (Rugg-Gunn et al., 2003). When MT MRI was combined with DWI, reductions in both MTR and ADC were found in the epileptic focus of patients (Ferini-Strambi et al., 2000). 

More advanced quantitation methods for MT MRI have been showm to be sensitive to white matter tracts and axonal density (Yamykh and Yuan, 2004) as well as being sensitive to the earliest events in stroke lesions (Jiang et al., 2001) including early detection of ruptures in the blood-brain barrier which may be susceptible to hemorrhagic transformation (Knight et al., 2005). 

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MLCT metal-to-ligand charge transfer MRI magnetic resonance imaging NIR near-infra red NMR nuclear magnetic resonance... 

IVCT = inter valence charge-transfer LMCT = ligand-to-metal charge-transfer MLCT = metal-to-ligand charge-transfer MRI = magnetic resonance imaging... 

Figure 50.11. Magnetization transfer MRI. A Off-resonance application of a saturation pulse will saturate the signal from macromolecules with short T2 (broad line) while leaving the narrow water resonance (center line) uneffected. B Saturation of macromolecules (spin pool A) causes reduction of the free water signal (spin pool B) measured as reduction in intensity of MRI (M /M g, ) inversely proportional to the exchange rate of free water with the water in the macromolecular hydration layer (k ) times the of free water (T ).

DTPA = diethylentetramine-penta-acetate FRET = Forster resonant energy transfer MRI = magnetic resonance imaging NIR = near infra-red PET = positron emission tomography. 

Beside classical MRI, based on the measurement of water abundance in tissues and variation of its relaxation rates, other techniques such as chemical exchange saturation transfer (CEST) and its improved form using paramagnetic compounds (PARACEST) are currently investigated to improve the potential of MRI diagnosis. 

The validation of CFD codes by comparison to reliable experiments is of the highest importance. Especially promising is the use of MRI methods to non-invasively provide flow fields and dispersion data. Major challenges will be to extend MRI and similar methods such as LDV and particle tracking to a wider range of conditions, and to develop noninvasive measurements of temperature to improve verification of heat transfer simulations. 

To facilitate international export, mangos are usually disinfested from insect larvae by either chemical or heat treatment. Unfortunately, heat treatments severe enough to kill the larvae can also damage the skin and pulp (mesocarp). Pulp symptoms include impaired starch degradation and development of internal cavities, which are manifest in MRI. Spin-echo image contrast showed the initiation of heat injury around vascular traces in the mesocarp possibly because they form a network for rapid heat transfer and/or retain heat... 

The saturation transfer is induced by the selective irradiation of the mobile protons of the probe with a proper radiofrequency field. When different pools of exchangeable protons are available, this modality enables the set-up of ratiometric methods in which a responsive PARACEST agent provides a MRI response no longer dependent on its absolute concentration (119-120). 

As important as calcium is probably iron [122]. Iron is the metal center of many essential proteins and enzymes, such as hemoglobin, an oxygen carrier, or peroxidase, that oxidizes hydrogen peroxide, or even the large family of cytochromes, which act as electron transfer proteins in many important biochemical processes [85]. New families of MRI contrast agents have been designed such that their relaxivity is iron concentration dependent [128-130]. The two latest are based on Gd(III) chelates (Fig. 20) but differ by the mechanism responsible for their iron sensitivity and will be described further. 

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