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 'Spoiled Gradient Echo Sequence' 
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Result : Searchterm 'Spoiled Gradient Echo Sequence' found in 1 term [] and 12 definitions [], (+ 10 Boolean[] results
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MRA - Claustrophobia - Artifacts - Devices - Hospitals - Implant and Prosthesis
 
Blood Oxygenation Level Dependent ContrastInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Functional MRI -
 
(BOLD) In MRI the changes in blood oxygenation level are visible. Oxyhaemoglobin (the principal haemoglobin in arterial blood) has no substantial magnetic properties, but deoxyhaemoglobin (present in the draining veins after the oxygen has been unloaded in the tissues) is strongly paramagnetic. It can thus serve as an intrinsic paramagnetic contrast agent in appropriately performed brain MRI. The concentration and relaxation properties of deoxyhaemoglobin make it a susceptibility , e.g. T2 relaxation effective contrast agent with little effect on T1 relaxation.
During activation of the brain, the oxygen consumption of the local tissue increase by approximately 5% with that the oxygen tension will decrease. As a consequence, after a short period of time vasodilatation occurs, resulting in a local increase of blood volume and flow by 20 - 40%. The incommensurate change in local blood flow and oxygen extraction increases the local oxygen level.
By using T2 weighted gradient echo EPI sequences, which are highly susceptibility sensitive and fast enough to capture the three-dimensional nature of activated brain areas will show an increase in signal intensity as oxyhaemoglobin is diamagnetic and deoxyhaemoglobin is paramagnetic. Other MR pulse sequences, such as spoiled gradient echo pulse sequences are also used.
As the effects are subtle and of the order of 2% in 1.5 T MR imaging, sophisticated methodology, paradigms and data analysis techniques have to be used to consistently demonstrate the effect.
As the BOLD effect is due to the deoxygenated blood in the draining veins, the spatial localization of the region where there is increased blood flow resulting in decreased oxygen extraction is not as precisely defined as the morphological features in MRI. Rather there is a physiological blurring, and is estimated that the linear dimensions of the physiological spatial resolution of the BOLD phenomenon are around 3 mm at best.
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• Related Searches:
    • Haemoglobin
    • T2 Relaxation
    • Blood Flow Imaging
    • Susceptibility
    • Perfusion Imaging
 
Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
  News & More:
A mechanistic computational framework to investigate the hemodynamic fingerprint of the blood oxygenation level-dependent signal
Tuesday, 29 August 2023   by analyticalsciencejournals.onlinelibrary.wiley.com    
The utility of texture analysis of kidney MRI for evaluating renal dysfunction with multiclass classification model
Tuesday, 30 August 2022   by www.nature.com    
MRI Technique Used to Identify Future Risk of Binge Drinking
Monday, 6 January 2020   by www.diagnosticimaging.com    
Gold Acupuncture Needle MRI Pain Discovery
Friday, 3 January 2014   by www.healthcmi.com    
MRI method for measuring MS progression validated
Thursday, 19 December 2013   by www.eurekalert.org    
MRI Resources 
MRI Centers - Sequences - Stimulator pool - Functional MRI - Blood Flow Imaging - Intraoperative MRI
 
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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• View the DATABASE results for 'Contrast Enhanced Magnetic Resonance Angiography' (14).Open this link in a new window


• View the NEWS results for 'Contrast Enhanced Magnetic Resonance Angiography' (2).Open this link in a new window.
 
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 
Online Books - Coils - Musculoskeletal and Joint MRI - Diffusion Weighted Imaging - Nerve Stimulator - Knee MRI
 
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:
  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 
Service and Support - Examinations - Veterinary MRI - Cardiovascular Imaging - RIS - Breast Implant
 
Fast Spoiled Grass Sequence with IR PreparationInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(IR-FSPGR) This sequence uses an inversion pulse followed by a spoiled low flip angle and short TR gradient echo train to collect all partition data. The 3D-IR-FSPGR uses centric ordering of Gz. The selected TI is also the effective TI. The centric reordering strategy can lead to image blurring if a steady state is not achieved quickly with low flip angles (less than 20°).
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MRI Resources 
Homepages - Quality Advice - Process Analysis - Image Quality - MRI Technician and Technologist Jobs - Spine MRI
 
Liver Acquisition with Volume AcquisitionInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(LAVA) The MRI technique LAVA is based on a 3 dimensional spoiled gradient echo pulse sequence. The optimized inversion pulse and a new fat suppression technique (called segmented special) provides enhanced image contrast and uniform fat suppression. Array spatial sensitivity encoding technique (ASSET) with partial data filling and shorter TR/TE enables to use short breath holds for dynamic liver imaging with multiple phases.
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• View the DATABASE results for 'Liver Acquisition with Volume Acquisition' (3).Open this link in a new window

 
Further Reading:
  Basics:
MR Field Notes
   by www.gehealthcare.com    
MRI Resources 
Homepages - Knee MRI - Blood Flow Imaging - Mobile MRI Rental - Jobs - Colonography
 
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