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Result : Searchterm 'T1 Time' found in 1 term [] and 14 definitions [], (+ 19 Boolean[] results
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Saturation Recovery
 
(SR) Particular type of partial saturation pulse sequence in which the preceding pulses leave the spins in a state of saturation, so that recovery at the time of the next pulse has taken place from an initial condition of no magnetization. A rare used MRI pulse sequence that generates a predominantly proton density dependent signal, basically employing a 90° RF excitation pulse, with a very long repetition time. With this technique T1 times can be measured faster than with inversion recovery pulse sequences.
This saturation recovery sequence consists of multiple 90° radio frequency (RF) pulses with a short repetition time. A spoiler gradient pulse dephases the longitudinal magnetization that remains after the first 90° radio frequency pulse. A repetition time interval after the application of this spoiling gradient turns an additional 90° pulse the new developed longitudinal magnetization into the transverse plane, followed by recording a gradient echo.
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• Related Searches:
    • Spectral Presaturation Inversion Recovery
    • Gradient Echo Sequence
    • Inversion Recovery
    • Partial Saturation
    • Suppression
 
Further Reading:
  Basics:
Contrast mechanisms in magnetic resonance imaging
2004   by www.iop.org    
MRI Resources 
Coils - Colonography - Safety pool - Image Quality - - Breast Implant
 
Short T1 Inversion RecoveryInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(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.
 
Images, Movies, Sliders:
 Sagittal Knee MRI Images STIR  Open this link in a new window
      

 
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• View the DATABASE results for 'Short T1 Inversion Recovery' (3).Open this link in a new window

 
Further Reading:
  Basics:
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    
  News & More:
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    
MRI Resources 
Corporations - Hospitals - Artifacts - Calculation - Fluorescence - Safety Products
 
Short T1-Relaxation Gastrointestinal AgentsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.
 
Protons in -CH2- groups, e.g., contained in fatty emulsions, mineral or vegetable oil or sucrose polyester, have a fast relaxation and short T1 time. These agents with short T1-relaxation, if used in gastrointestinal imaging, produce bright signal intensities in the intestine on T1 weighted sequences. Palatable oil emulsions can produce appropriate contrast opacification of the stomach as well as the small bowel, but caused by absorption in the distal small bowel these materials are not suitable for use in MRI colonoscopy.

See also Positive Oral Contrast Agents and Gastrointestinal Paramagnetic Contrast Agents.
 
Images, Movies, Sliders:
 MR Colonography Gadolinium per Rectum  Open this link in a new window
      

Courtesy of  Robert R. Edelman
 
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• View the DATABASE results for 'Short T1-Relaxation Gastrointestinal Agents' (2).Open this link in a new window

Searchterm 'T1 Time' was also found in the following services: 
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Superparamagnetic Iron OxideInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.
 
(SPIO) Relatively new types of MRI contrast agents are superparamagnetic iron oxide-based colloids (median diameter greater than 50nm). These compounds consist of nonstoichiometric microcrystalline magnetite cores, which are coated with dextrans (in ferumoxide) or siloxanes (in ferumoxsil). After injection they accumulate in the reticuloendothelial system (RES) of the liver (Kupffer cells) and the spleen. At low doses circulating iron decreases the T1 time of blood, at higher doses predominates the T2* effect.
SPIO agents are much more effective in MR relaxation than paramagnetic agents. Since hepatic tumors either do not contain RES cells or their activity is reduced, the contrast between liver and lesion is improved. Superparamagnetic iron oxides cause noticeable shorter T2 relaxation times with signal loss in the targeted tissue (e.g., liver and spleen) with all standard pulse sequences. Magnetite, a mixture of FeO and Fe2O3, is one of the used iron oxides. FeO can be replaced by Fe3O4.
Use of these colloids as tissue specific contrast agents is now a well-established area of pharmaceutical development. Feridex®, Endorem™, GastroMARK®, Lumirem®, Sinerem®, Resovist® and more patents pending tell us that the last word in this area is not said.
Some remarkable points using SPIO:
A minimum delay of about 10 min. between injection (or infusion) and MR imaging, extends the examination time.
Cross-section flow void in narrow blood vessels may impede the differentiation from small liver lesions.
Aortic pulsation artifacts become more pronounced.


See also Superparamagnetism, Superparamagnetic Contrast Agents and Classifications, Characteristics, etc..
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• View the DATABASE results for 'Superparamagnetic Iron Oxide' (32).Open this link in a new window


• View the NEWS results for 'Superparamagnetic Iron Oxide' (3).Open this link in a new window.
 
Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
  News & More:
How to stop using gadolinium chelates for magnetic resonance imaging: clinical-translational experiences with ferumoxytol
Saturday, 5 February 2022   by www.ncbi.nlm.nih.gov    
Polysaccharide-Core Contrast Agent as Gadolinium Alternative for Vascular MR
Monday, 8 March 2021   by www.diagnosticimaging.com    
Poly (dopamine) coated superparamagnetic iron oxide nanocluster for noninvasive labeling, tracking, and targeted delivery of adipose tissue-derived stem cells
Tuesday, 5 January 2016   by www.nature.com    
Longitudinal MRI contrast enhanced monitoring of early tumour development with manganese chloride (MnCl2) and superparamagnetic iron oxide nanoparticles (SPIOs) in a CT1258 based in vivo model of prostate cancer
Wednesday, 11 July 2012   by www.biomedcentral.com    
MRI Resources 
Nerve Stimulator - Artifacts - Cardiovascular Imaging - Stent - Contrast Agents - General
 
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    
  News & More:
MRI's inside story
Thursday, 4 December 2003   by www.economist.com    
MRI Resources 
Online Books - Liver Imaging - Implant and Prosthesis pool - Diffusion Weighted Imaging - Contrast Enhanced MRI - Developers
 
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