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Magnetization Transfer
 
(MT) Magnetization Transfer was accidentally discovered by Wolff and Balaban in 1989. Conventional MRI is based on the differences in T1, T2 and the proton density (water content and the mobility of water molecules) in tissue; it relies primarily on free (bulk) water protons. The T2 relaxation times are greater than 10 ms and detectable. The T2 relaxation times of protons associated with macromolecules are less then 1 ms and not detectable in MRI.
Magnetization Transfer Imaging (MTI) is based on the magnetization interaction (through dipolar and/or chemical exchange) between bulk water protons and macromolecular protons. By applying an off resonance radio frequency pulse to the macromolecular protons, the saturation of these protons is then transferred to the bulk water protons. The result is a decrease in signal (the net magnetization of visible protons is reduced), depending on the magnitude of MT between tissue macromolecules and bulk water. With MTI, the presence or absence of macromolecules (e.g. in membranes, brain tissue) can be seen.
The magnetization transfer ratio (MTR) is the difference in signal intensity with or without MT.

See also Magnetization Transfer Contrast.
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• View the DATABASE results for 'Magnetization Transfer' (7).Open this link in a new window

 
Further Reading:
  Basics:
MICRO-STRUCTURAL QUANTITIES - DIFFUSION, MAGNETISATION DECAY, MAGNETISATION TRANSFER AND PERMEABILITY(.pdf)
   by www.dundee.ac.uk    
The Basics of MRI
   by www.cis.rit.edu    
  News & More:
Gold-manganese nanoparticles for targeted diagnostic and imaging
Thursday, 12 November 2015   by www.nanowerk.com    
Magnetization Transfer Magnetic Resonance Imaging of Hepatic Tumors(.pdf)
   by www.nci.edu.eg    
Magnetization Transfer Contrast
 
(MTC) This MRI method increases the contrast by removing a portion of the total signal in tissue. An off resonance radio frequency (RF) pulse saturates macromolecular protons to make them invisible (caused by their ultra-short T2* relaxation times). The MRI signal from semi-solid tissue like brain parenchyma is reduced, and the signal from a more fluid component like blood is retained.
E.g., saturation of broad spectral lines may produce decreases in intensity of lines not directly saturated, through exchange of magnetization between the corresponding states; more closely coupled states will show a greater resulting intensity change. Magnetization transfer techniques make demyelinated brain or spine lesions (as seen e.g. in multiple sclerosis) better visible on T2 weighted images as well as on gadolinium contrast enhanced T1 weighted images.
Off resonance makes use of a selection gradient during an off resonance MTC pulse. The gradient has a negative offset frequency on the arterial side of the imaging volume (caudally more off resonant and cranially less off resonant). The net effect of this type of pulse is that the arterial blood outside the imaging volume will retain more of its longitudinal magnetization, with more vascular signal when it enters the imaging volume. Off resonance MTC saturates the venous blood, leaving the arterial blood untouched.
On resonance has no effect on the free water pool but will saturate the bound water pool and is the difference in T2 between the pools. Special binomial pulses are transmitted causing the magnetization of the free protons to remain unchanged. The z-magnetization returns to its original value. The spins of the bound pool with a short T2 experience decay, resulting in a destroyed magnetization after the on resonance pulse.

See also Magnetization Transfer.
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• View the DATABASE results for 'Magnetization Transfer Contrast' (5).Open this link in a new window

 
Further Reading:
  News & More:
MRI of the Human Eye Using Magnetization Transfer Contrast Enhancement
   by www.iovs.org    
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Magnetization Value
 
(Mo) Equilibrium value of the magnetization;; directed along the direction of the static magnetic field. Proportional to spin density (N).
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• View the DATABASE results for 'Magnetization Value' (3).Open this link in a new window

Magnetization Vector
 
The integration of all the individual nuclear magnetic moments, which have a positive magnetization value at equilibrium versus those in a random state.
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• View the DATABASE results for 'Magnetization Vector' (18).Open this link in a new window

Magnetohydrodynamic Effect
 
This effect is an additional electrical charge generated by ions in blood (loaded particles) moving perpendicular to the magnetic field. At 1.5 T, no significant changes are expected; at 6.0 T a 10% blood pressure change is expected. A blood pressure increase is predicted theoretically for a field of 10 T. This is claimed to be caused by interaction of induced electrical potentials and currents within a solution, e.g. blood, and an electrical volume force causing a retardation in the direction opposite to the fluid flow. This decrease in blood flow-velocity must be compensated for by an elevation in pressure.
Static magnetic field gradients of 0.01 T/cm (100 G/cm) make no significant difference in the membrane transport processes. The influence of a static magnetic field upon erythrocytes is not sufficient to provoke sedimentation, as long as there is a normal blood circulation.
mri safety guidance
MRI Safety Guidance
The magnetohydrodynamic effect which results from a voltage occurring across a vessel in a magnetic field, is irrelevant at the field strengths used.
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• View the DATABASE results for 'Magnetohydrodynamic Effect' (3).Open this link in a new window

 
Further Reading:
  News & More:
Measuring magnetic force field distributions in microfluidic devices: Experimental and numerical approaches
Saturday, 2 December 2023   by analyticalsciencejournals.onlinelibrary.wiley.com    
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