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Result : Searchterm 'T2*' found in 2 terms [] and 41 definitions []
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Contrast Enhanced Magnetic Resonance AngiographyInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - MRA -
 
(CE MRA) Contrast enhanced MR angiography is based on the T1 values of blood, the surrounding tissue, and paramagnetic contrast agent.
T1-shortening contrast agents reduces the T1 value of the blood (approximately to 50 msec, shorter than that of the surrounding tissues) and allow the visualization of blood vessels, as the images are no longer dependent primarily on the inflow effect of the blood. Contrast enhanced MRA is performed with a short TR to have low signal (due to the longer T1) from the stationary tissue, short scan time to facilitate breath hold imaging, short TE to minimize T2* effects and a bolus injection of a sufficient dose of a gadolinium chelate.
Images of the region of interest are performed with 3D spoiled gradient echo pulse sequences. The enhancement is maximized by timing the contrast agent injection such that the period of maximum arterial concentration corresponds to the k-space acquisition. Different techniques are used to ensure optimal contrast of the arteries e.g., bolus timing, automatic bolus detection, bolus tracking, care bolus. A high resolution with near isotropic voxels and minimal pulsatility and misregistration artifacts should be striven for. The postprocessing with the maximum intensity projection (MIP) enables different views of the 3D data set.
Unlike conventional MRA techniques based on velocity dependent inflow or phase shift techniques, contrast enhanced MRA exploits the gadolinium induced T1-shortening effects. CE MRA reduces or eliminates most of the artifacts of time of flight angiography or phase contrast angiography. Advantages are the possibility of in plane imaging of the blood vessels, which allows to examine large parts in a short time and high resolution scans in one breath hold. CE MRA has found a wide acceptance in the clinical routine, caused by the advantages:
3D MRA can be acquired in any plane, which means that greater vessel coverage can be obtained at high resolution with fewer slices (aorta, peripheral vessels);
the possibility to perform a time resolved examination (similarly to conventional angiography);
no use of ionizing radiation; paramagnetic agents have a beneficial safety.


 
Images, Movies, Sliders:
 CE-MRA of the Carotid Arteries  Open this link in a new window
    
SlidersSliders Overview

 CE MRA of the Aorta  Open this link in a new window
    
SlidersSliders Overview

 CE-MRA of the Carotid Arteries Colored MIP  Open this link in a new window
    
SlidersSliders Overview

 
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• Related Searches:
    • Contrast Enhanced MRI
    • Cardiovascular Imaging
    • Contrast Agents
    • Contrast Enhanced MR Venography
    • Magnetic Resonance Angiography MRA
 
Further Reading:
  Basics:
Contrast-Enhanced MR Angiography(.pdf)
   by ric.uthscsa.edu    
CONTRAST ENHANCED MR ANGIOGRAPHY – PRINCIPLES, APPLICATIONS, TIPS AND PITFALLS(.pdf)
  News & More:
CONTRAST-ENHANCED MRA OF THE CAROTIDS(.pdf)
PERIPHERAL VASCULAR MAGNETIC RESONANCE ANGIOGRAPHY(.pdf)
CONTRAST ENHANCED MRI OF THE LIVER STATE-OF-THE-ART(.pdf)
MRI Resources 
MR Guided Interventions - Used and Refurbished MRI Equipment - Spectroscopy - Software - Knee MRI - Universities
 
Dephasing
 
The spins (protons) go out of phase in the transverse plane when the Rf pulse is switched of. This dephasing is due to static magnetic field inhomogeneities intrinsic (i.e. susceptibility changes at tissue interfaces) and extrinsic (i.e. field inhomogeneities of the main magnetic field) to the examined object.
See also T2*.
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• View the DATABASE results for 'Dephasing' (26).Open this link in a new window

 
Further Reading:
  Basics:
Spin echoes, CPMG and T2 relaxation - Introductory NMR & MRI from Magritek
2013   by www.azom.com    
Comparison of Fast Spin-Echo Versus Conventional Spin-Echo MRI forEvaluating Meniscal Tears
June 2005   by www.ajronline.org    
Contrast mechanisms in magnetic resonance imaging
2004   by www.iop.org    
MRI Resources 
Spine MRI - Education pool - General - Safety pool - Diffusion Weighted Imaging - Artifacts
 
Dy-DOTA-4AmCEInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Short name: Dy-DOTA-4AmCE, central moiety: Dy2+, contrast effect: T2*enhanced
Dy-DOTA-4AmCE, a macrocyclic complex is characterized by a very slow water exchange, a complex compared with several Dy-DTPA derivatives known for their efficacy as T2 contrast agents at high magnetic fields.

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Further Reading:
  Basics:
Dysprosium
   by www.scescape.net    
Searchterm 'T2*' was also found in the following services: 
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News  (2)  Resources  (1)  Forum  (11)  
 
Fast Low Angle ShotInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(FLASH) A fast sequence producing signals called gradient echo with low flip angles. FLASH sequences are modifications, which incorporate or remove the effects of transverse coherence respectively.
FLASH uses a semi-random spoiler gradient after each echo to spoil the steady state (to destroy any remaining transverse magnetization) by causing a spatially dependent phase shift. The transverse steady state is spoiled but the longitudinal steady state depends on the T1 values and the flip angle. Extremely short TR times are possible, as a result the sequence provides a mechanism for gaining extremely high T1 contrast by imaging with TR times as brief as 20 to 30 msec while retaining reasonable signal levels. It is important to keep the TE as short as possible to suppress susceptibility artifacts.
The T1 contrast depends on the TR as well as on flip angle, with short TE.
Small flip angles and short TR results in proton density, and long TR in T2* weighting.
With large flip angles and short TR result T1 weighted images.

TR and flip angle adjustment:

TR 3000 ms, Flip Angle 90°
TR 1500 ms, Flip Angle 45°
TR 700 ms, Flip Angle 25°
TR 125 ms, Flip Angle 10°
The apparent ability to trade TR against flip angle for purposes of contrast and the variation in SNR as the scan time (TR) is reduced.
See also Gradient Echo Sequence.

 
Images, Movies, Sliders:
 Fetus (Brain) and Dermoid in Mother  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 
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• View the DATABASE results for 'Fast Low Angle Shot' (5).Open this link in a new window

 
Further Reading:
  Basics:
Real-time MRI: recent advances using radial FLASH
Wednesday, 4 April 2012   by www.futuremedicine.com    
  News & More:
Motion Compensation in MR Imaging
   by ccn.ucla.edu    
Turbo-FLASH Based Arterial Spin Labeled Perfusion MRI at 7 T
Thursday, 20 June 2013   by www.plosone.org    
Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CT
2000   by www.ncbi.nlm.nih.gov    
MRI Resources 
Online Books - Open Directory Project - Education pool - Mass Spectrometry - Journals - Hospitals
 
Gadopentetate DimeglumineInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Short name: Gd-DTPA, generic name: Gadopentetate dimeglumine, chemical compound: Gadolinium-diethylenetriaminepentaacetic acid
Gadopentetate dimeglumine was introduced in 1981, as the first paramagnetic MRI contrast agent (ionic). The Gd-induced dipole dipole interactions lead to shortening of T1, which results in contrast enhancement on T1 weighted images. The used metal ion Gd3+ (gadolinium) is toxic, and therefore bound in the renally excreted DTPA chelate, a very stable complex. The Gd-complex also induce susceptibility effects, as a result of the magnetic field gradient between the contrast agent in the blood vessels and the surrounding tissue, that lead to shortening of T2 or T2*.
Following intravenous administration, the compound is distributed rapidly in the extracellular space and is eliminated unchanged by glomerular filtration via the kidneys. Up to 6 hours, post injection an average of 83% of the dose is eliminated renal.
See also Magnevist®, Gadolinium and Contrast Agents.

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• View the DATABASE results for 'Gadopentetate Dimeglumine' (5).Open this link in a new window

 
Further Reading:
  Basics:
Magnevist Package Insert
2000
Gadopentetic acid
   by en.wikipedia.org    
  News & More:
PRAC concludes assessment of gadolinium agents used in body scans and recommends regulatory actions, including suspension for some marketing authorisations
Friday, 10 March 2017   by www.satprnews.com    
EMA's final opinion confirms restrictions on use of linear gadolinium agents in body scans
Friday, 21 July 2017   by www.ema.europa.eu    
MRI Resources 
General - Stent - Abdominal Imaging - Examinations - Lung Imaging - Pathology
 
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