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Relaxation Rates
 
Reciprocals of the relaxation times, T1 and T2 (R1 = 1/T1 and R2 = 1/T2). There is often a linear relation between the concentration of MR contrast agents and the resulting change in relaxation rate. The rate of relaxation is influenced by molecules with protons that are tumbling. A slower tumble rate will result in faster relaxation rate (shorter relaxation time). Due to the molecular structure of fat with its larger size than water, fat will tumble slower than water molecules. The slower tumble rate of fat enables a faster relaxation rate.
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• View the DATABASE results for 'Relaxation Rates' (5).Open this link in a new window

 
Further Reading:
  Basics:
Evaluation of Absorbed Dose by MRI Read-Out
Saturday, 18 November 2017   by www.jstage.jst.go.jp    
  News & More:
Multimodal Nanoparticles for Quantitative Imaging(.pdf)
Tuesday, 13 December 2011   by alexandria.tue.nl    
Relaxation TimeForum -
there are related threads
 
After RF excitation the spins will tend to return to their equilibrium distribution in which there is no transverse magnetization and the longitudinal magnetization is at its maximum value and oriented in the direction of the static magnetic field. The transverse magnetization decays toward zero with a characteristic time constant T2, and the longitudinal magnetization returns toward equilibrium with a characteristic time constant T1.
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• View the DATABASE results for 'Relaxation Time' (44).Open this link in a new window

 
Further Reading:
  Basics:
Musculoskeletal MRI at 3.0 T: Relaxation Times and Image Contrast
Sunday, 1 August 2004   by www.ajronline.org    
  News & More:
New technique could allow for safer, more accurate heart scans
Thursday, 10 December 2015   by www.gizmag.com    
MRI Resources 
Absorption and Emission - Stent - Hospitals - Movies - Spine MRI - Mobile MRI
 
Relaxivity
 
The ability of magnetic compounds to increase the relaxation rates of the surrounding water proton spins.
Relaxivity is used to improve the contrast of the image, and to study tissue specific areas where the contrast agent better diffuses or to perform functional magnetic resonance imaging.
The relaxivity of MRI contrast agents depends on the molecular structure and kinetic of the complex. To increase the number of water molecules that are in the inner sphere of the complex, or to slow down the molecular rotational correlation time, are possibilities to improve the water relaxivity.
Relaxivity units (r1, r2) are mM-1 * sec-1 (at varying temperatures).
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• View the NEWS results for 'Relaxivity' (2).Open this link in a new window.

• View the DATABASE results for 'Relaxivity' (51).Open this link in a new window

 
Further Reading:
  News & More:
Measurements of the relaxivity of gadolinium chelates in tissues in vivo(.pdf)
2001   by cds.ismrm.org    
Relaxometry
 
Relaxation time is a general physics concept for the characteristic time in which a system relaxes under certain changes in external conditions. Relaxometry is the theory of relaxation times (spin lattice (T1) and spin spin relaxation (T2)), and their dependence on physical parameters such as magnetic field strength, molecular structure, temperature, pH, and the presence and type of relaxation agents.
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• View the NEWS results for 'Relaxometry' (1).Open this link in a new window.
 
Further Reading:
  Basics:
Measurements of the relaxivity of gadolinium chelates in tissues in vivo(.pdf)
2001   by cds.ismrm.org    
  News & More:
Imagion (ASX:IBX) share price up 1,166% in a year pursuing adiation-freeā„¢ cancer tech
Monday, 29 March 2021   by www.fool.com.au    
Repetition Time
 
(TR) The amount of time that exists between successive pulse sequences applied to the same slice.
It is delineated by initiating the first RF pulse of the sequence then repeating the same RF pulse at a time t. Variations in the value of TR have an important effect on the control of image contrast characteristics. TR is also a major factor in total scan time.

See also Scan Time and Image Contrast Characteristics.
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• View the DATABASE results for 'Repetition Time' (33).Open this link in a new window

 
Further Reading:
  Basics:
Magnetic resonance imaging
   by www.scholarpedia.org    
What MRI Sequences Produce the Highest Specific Absorption Rate (SAR), and Is There Something We Should Be Doing to Reduce the SAR During Standard Examinations?
Thursday, 16 April 2015   by www.ajronline.org    
  News & More:
A short-TR single-echo spin-echo breath-hold method for assessing liver T2
Sunday, 10 December 2023   by link.springer.com    
MRI Resources 
Jobs - Lung Imaging - Breast Implant - Devices - Implant and Prosthesis - Patient Information
 
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MRI is trending to low field magnets :
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