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Spin Lattice Relaxation Time
 
(T1) The spin lattice relaxation time (also called longitudinal relaxation time and T1 Time) is a spin property, whereby the value changes between different tissues. By the spin lattice relaxation process, the longitudinal magnetization Mz achieve the equilibrium value Mz0. The T1 time constant is an exponential approach toward Mz0.
The equation for the magnetization at a time t will be (if at t=0 the longitudinal magnetization is Mz0):
Mz(t) = M0+(Mz (0) - Mz0) exp(t/T1)
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    • Longitudinal Relaxation Time
    • Contrast Enhanced MRI
    • Longitudinal Relaxation
    • Spin Lattice Relaxation
    • Short T1 Inversion Recovery
 
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Electron Spin Resonance
   by hyperphysics.phy-astr.gsu.edu    
  News & More:
MRI's inside story
Thursday, 4 December 2003   by www.economist.com    
MULTIEXPONENTIAL PROTON SPIN-SPIN RELAXATION IN MAGNETIC RESONANCE IMAGING OF HUMAN BRAIN TUMORS
Friday, 26 March 1999   by www.dkfz-heidelberg.de    
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Short T1 Inversion RecoveryInfoSheet: - Sequences - 
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(STIR) Also called Short Tau (t) (inversion time) Inversion Recovery. STIR is a fat suppression technique with an inversion time t = T1 ln2 where the signal of fat is zero (T1 is the spin lattice relaxation time of the component that should be suppressed). To distinguish two tissue components with this technique, the T1 values must be different. Fluid Attenuation Inversion Recovery (FLAIR) is a similar technique to suppress water.
Inversion recovery doubles the distance spins will recover, allowing more time for T1 differences. A 180° preparation pulse inverts the net magnetization to the negative longitudinal magnetization prior to the 90° excitation pulse. This specialized application of the inversion recovery sequence set the inversion time (t) of the sequence at 0.69 times the T1 of fat. The T1 of fat at 1.5 Tesla is approximately 250 with a null point of 170 ms while at 0.5 Tesla its 215 with a 148 ms null point. At the moment of excitation, about 120 to 170 ms after the 180° inversion pulse (depending of the magnetic field) the magnetization of the fat signal has just risen to zero from its original, negative, value and no fat signal is available to be flipped into the transverse plane.
When deciding on the optimal T1 time, factors to be considered include not only the main field strength, but also the tissue to be suppressed and the anatomy. In comparison to a conventional spin echo where tissues with a short T1 are bright due to faster recovery, fat signal is reversed or darkened. Because body fluids have both a long T1 and a long T2, it is evident that STIR offers the possibility of extremely sensitive detection of body fluid. This is of course, only true for stationary fluid such as edema, as the MRI signal of flowing fluids is governed by other factors.

See also Fat Suppression and Inversion Recovery Sequence.
 
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 Sagittal Knee MRI Images STIR  Open this link in a new window
      

 
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Can Short Tau Inversion Recovery (STIR) Imaging Be Used as a Stand-Alone Sequence To Assess a Perianal Fistulous Tract on MRI? A Retrospective Cohort Study Comparing STIR and T1-Post Contrast Imaging
Wednesday, 17 January 2024   by www.cureus.com    
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Generating Virtual Short Tau Inversion Recovery (STIR) Images from T1- and T2-Weighted Images Using a Conditional Generative Adversarial Network in Spine Imaging
Wednesday, 25 August 2021
Short tau inversion recovery (STIR) after intravenous contrast agent administration obscures bone marrow edema-like signal on forefoot MRI
Tuesday, 13 July 2021   by www.springermedizin.de    
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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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Further Reading:
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Measurements of the relaxivity of gadolinium chelates in tissues in vivo(.pdf)
2001   by cds.ismrm.org    
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Imagion (ASX:IBX) share price up 1,166% in a year pursuing adiation-free™ cancer tech
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T1 Relaxation
 
The return to equilibrium (high energy protons returns to the low energy state) within the lattice is named the T1, spin lattice or longitudinal relaxation. During the time T1, the spinning protons realign with the external magnetic field with an exchange of their energy, resulting in heat. The value of the T1 time depends of the tissues ability for energy exchange.

See also Longitudinal Relaxation Time.
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• View the DATABASE results for 'T1 Relaxation' (18).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    
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MRI's inside story
Thursday, 4 December 2003   by www.economist.com    
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T1 TimeForum -
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The T1 relaxation time (also called spin lattice or longitudinal relaxation time), is a biological parameter that is used in MRIs to distinguish between tissue types. This tissue-specific time constant for protons, is a measure of the time taken to realign with the external magnetic field. The T1 constant will indicate how quickly the spinning nuclei will emit their absorbed RF into the surrounding tissue.
As the high-energy nuclei relax and realign, they emit energy which is recorded to provide information about their environment. The realignment with the magnetic field is termed longitudinal relaxation and the time in milliseconds required for a certain percentage of the tissue nuclei to realign is termed 'Time 1' or T1. Starting from zero magnetization in the z direction, the z magnetization will grow after excitation from zero to a value of about 63% of its final value in a time of T1. This is the basic of T1 weighted images.
The T1 time is a contrast determining tissue parameter. Due to the slow molecular motion of fat nuclei, longitudinal relaxation occurs rather rapidly and longitudinal magnetization is regained quickly. The net magnetic vector realigns with B0 leading to a short T1 time for fat.
Water is not as efficient as fat in T1 recovery due to the high mobility of the water molecules. Water nuclei do not give up their energy to the lattice (surrounding tissue) as quickly as fat, and therefore take longer to regain longitudinal magnetization, resulting in a long T1 time.

See also T1 Weighted Image, T1 Relaxation, T2 Weighted Image, and Magnetic Resonance Imaging MRI.
 
Images, Movies, Sliders:
 Anatomic MRI of the Knee 2  Open this link in a new window
    
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 Breast MRI Images T2 And T1  Open this link in a new window
 Brain MRI Images T1  Open this link in a new window
      

 
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• View the DATABASE results for 'T1 Time' (15).Open this link in a new window

 
Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
A practical guideline for T1 reconstruction from various flip angles in MRI
Saturday, 1 October 2016   by journals.sagepub.com    
Magnetic resonance imaging - From Wikipedia, the free encyclopedia.
   by en.wikipedia.org    
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New technique could allow for safer, more accurate heart scans
Thursday, 10 December 2015   by www.gizmag.com    
Rockland Technimed: Tissue Viability Imaging
Saturday, 15 December 2007   by www.onemedplace.com    
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