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Result : Searchterm 'Blood Flow Imaging' found in 1 term [] and 0 definition [], (+ 19 Boolean[] results
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Blood Flow ImagingMRI Resource Directory:
 - Blood Flow Imaging -
 
MR imaging techniques capable to provide maps of cerebral activity. All these techniques are based on indirect assessment of local cerebral haemodynamics that have been demonstrated to be closely related to cerebral activity.
Two kinds of techniques have been developed:
based on the assessment of the decrease in the content of deoxyhaemoglobin in local activated tissue that can be revealed as an increase of signal on T2* and T2 weighted sequences in which deoxyhaemoglobin has low signal (see Blood Oxygenation Level Dependent Contrast)
based on the time of flight or flow-related enhancement that is revealed either directly with T1 weighted images or through the use of modified angiographic bolus tracking techniques.

 
Images, Movies, Sliders:
 Circle of Willis, Time of Flight, MIP  Open this link in a new window
    
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• Related Searches:
    • Velocity Encoding
    • Black Blood MRA
    • Blood Oxygenation Level Dependent Contrast
    • Magnetic Resonance Angiography MRA
    • Brain MRI
 
Further Reading:
  News & More:
Turbo-FLASH Based Arterial Spin Labeled Perfusion MRI at 7 T
Thursday, 20 June 2013   by www.plosone.org    
Non-invasive MRI technique distinguishes between Alzheimer's and frontotemporal dementia
Saturday, 18 June 2005   by www.eurekalert.org    
MRI Resources 
Functional MRI - Cardiovascular Imaging - Online Books - MRI Centers - Hospitals - Mobile MRI
 
Arterial Spin LabelingInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(ASL) A MR image can be sensitized to the effect of inflowing blood spins if those spins are in a different magnetic state to that of the static tissue. Techniques known as ASL techniques uses this idea by magnetically labeling blood flowing into the slices of interest. Contrast agents are not required for these techniques. This perfusion measurement is completely noninvasive.
Blood flowing into the imaging slice exchanges with tissue water, altering the tissue magnetization. A perfusion-weighted image can be generated by the subtraction of an image in which inflowing spins have been labeled from an image in which spin labeling has not been performed. Quantitative perfusion maps can be calculated if other parameters (such as tissue T1 and the efficiency of spin labeling) also are measured.

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• View the DATABASE results for 'Arterial Spin Labeling' (5).Open this link in a new window


• View the NEWS results for 'Arterial Spin Labeling' (3).Open this link in a new window.
 
Further Reading:
  Basics:
Measuring Cerebral Blood Flow Using Magnetic Resonance Imaging Techniques
1999   by www.stanford.edu    
  News & More:
Ischemic Stroke: Collateral Blood Vessels Detected by Arterial Spin Labeling MRI Correlates With Good Neurological Outcome
Thursday, 30 March 2017   by medicalresearch.com    
Turbo-FLASH Based Arterial Spin Labeled Perfusion MRI at 7 T
Thursday, 20 June 2013   by www.plosone.org    
Non-invasive MRI technique distinguishes between Alzheimer's and frontotemporal dementia
Saturday, 18 June 2005   by www.eurekalert.org    
MRI Resources 
Online Books - Nerve Stimulator - Spectroscopy - Developers - Blood Flow Imaging - Software
 
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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• View the DATABASE results for 'Blood Oxygenation Level Dependent Contrast' (6).Open this link in a new window

 
Further Reading:
  Basics:
IMAGE CONTRAST IN MRI(.pdf)
   by www.assaftal.com    
High-Resolution, Spin-Echo BOLD, and CBF fMRI at 4 and 7 T(.pdf)
October 2002   by otg.downstate.edu    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
  News & More:
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    
BOLD MRI measures connectivity deficits related to MS
July 2002
Searchterm 'Blood Flow Imaging' was also found in the following services: 
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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
    
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 CE MRA of the Aorta  Open this link in a new window
    
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 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 
Education pool - Stent - Musculoskeletal and Joint MRI - Service and Support - Artifacts - Research Labs
 
Double Inversion Recovery T1 MeasurementInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(DIR or DIRT1) Double inversion recovery T1 measurement is a T1 weighted black blood MRA sequence in which the signal from blood is suppressed. The inversion time to suppress blood is described as the duration between the initial inversion pulse and time point that the longitudinal magnetization of blood reaches the zero point. The readout starts at the blood suppression inversion time (BSP TI) and blood in the imaging slice gives no signal. This inversion time is around 650 ms with a 60 beat per minute heart rate at 1.5 T.
The TI can be decreased by using a wider receive bandwidth, shorter echo train length and/or narrow trigger window. Wide bandwidth also decreases the blurring caused by long echo trains at the expense of signal to noise ratio. In case of in plane or slow flow the suppression of the signal from blood may be incomplete. With increased TE or change of the image plane the blood suppression can be improved.
Double inversion recovery is a breath hold technique with one image per acquisition used in cardiovascular imaging. The patient is instructed to hold the breath in expiration (if not possible also inspiration can be taken), so that the end diastolic volume in the cardiac chambers would be the same during entire scanning. DIR provides fine details of the boundary between the lumen and the wall of the cardiac chambers and main vascular and heart structures, pericardium, and mediastinal tissues.
 
Images, Movies, Sliders:
 Normal Dual Inversion Fast Spin-echo  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 
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• View the DATABASE results for 'Double Inversion Recovery T1 Measurement' (2).Open this link in a new window

MRI Resources 
Safety pool - MRI Training Courses - Collections - Liver Imaging - Examinations - Databases
 
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