Magnetic Resonance - Technology Information Portal Welcome to MRI Technology••
Info
  Sheets


Out-
      side
 



 
 'Gradient Echo Sequence' 
SEARCH FOR    
 
  2 3 5 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Result : Searchterm 'Gradient Echo Sequence' found in 5 terms [] and 80 definitions []
previous     61 - 65 (of 85)     next
Result Pages : [1]  [2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17]
Searchterm 'Gradient Echo Sequence' was also found in the following services: 
spacer
News  (1)  Resources  (1)  Forum  (3)  
 
Multi Echo Data Image CombinationInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(MEDIC) MEDIC is a heavily T2* weighted spoiled gradient echo sequence with multiple echoes. MEDIC uses a series of identically phase encoded gradient echoes, sampled per line in k-space. Unipolar frequency encoding gradients are used to achieve flow compensation and to avoid off resonance effects. For each echo the magnitude images are reconstructed and postprocessed by using a sum of squares algorithm to improve the signal to noise ratio. The increased receiver bandwidth reduces the T2* effects and impairment of the spatial resolution.
The multi echo data image combination sequence is potentially useful in imaging of cartilage in joints.
spacer
MRI Resources 
Pacemaker - Hospitals - Mobile MRI - Developers - Blood Flow Imaging - Pathology
 
Multiple Echo Single ShotInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(MESS) See Multiple Echo Imaging, Single Shot Technique and Ultrafast Gradient Echo Sequence.
spacer
MRI Resources 
Universities - MRI Training Courses - Functional MRI - MRA - Journals - Chemistry
 
Myocardial Late Enhancement
 
(LE) Myocardial late enhancement in contrast enhanced cardiac MRI has the ability to precisely delineate myocardial scar associated with coronary artery disease. Viability imaging implies evaluating infarcted myocardium to see whether there is enough viable tissue available for revascularization. The reversal of myocardial dysfunction is particularly relevant in patients with depressed ventricular function because revascularization improves long-term survival. In comparison to SPECT and PET imaging, myocardial late enhancement MRI demonstrates areas of delayed enhancement exactly in correlation with the infarcted region.
Viability on cardiac MRI (CMR) is based on the fact that all infarcts enhance vividly 10-15 minutes after the administration of intravenous paramagnetic contrast agents. This enhancement represents the accumulation of gadolinium in the extracellular space, due to the loss of membrane integrity in the infarcted tissue. This phenomenon of delayed hyperenhancement has been proven to correlate with the actual extent of the infarct.
MRI myocardial late enhancement can quantify the size, location and transmural extent of the infarct. If the transmural extent of the infarct (region of enhancement on MRI) is less than 50% of the wall thickness, there will be improved contractility in that segment following revascularization. In areas of hypokinesia, if there is a rim of "black" or non-infarcted myocardium that is not contracting well, it indicates the presence of hibernating myocardium, which is likely to improve after revascularization of the artery supplying that particular territory.
The total duration of a myocardial late enhancement MR imaging protocol for viability is approximately 30 minutes, including scout images, first-pass images, cine images in two planes, and delayed myocardial enhancement images. In order to assess viable myocardium, the gadolinium contrast agent is injected at a dose of 0.15 to 0.2 mmol/kg. After about 10 minutes, short axis and long axis views (see cardiac axes) of the heart are obtained using an inversion prepared ECG gated gradient echo sequence. The inversion pulse is adjusted to suppress normal myocardium. Areas of nonviable myocardium retain extremely high signal intensity, black areas show normal tissue.

For Ultrasound Imaging (USI) see Myocardial Contrast Echocardiography at US-TIP.com.
spacer

• View the DATABASE results for 'Myocardial Late Enhancement' (6).Open this link in a new window

 
Further Reading:
  Basics:
A Guide To Cardiac Imaging
   by www.simplyphysics.com    
  News & More:
The heart reacts in two distinct phases after myocardial
Saturday, 22 November 2014   by www.betawired.com    
Prediction of Myocardial Viability by MRI
1999   by circ.ahajournals.org    
Geron Demonstrates hESC-derived cardiomyocytes improve heart function after myocardial infarction
Monday, 27 August 2007   by www.brightsurf.com    
Searchterm 'Gradient Echo Sequence' was also found in the following services: 
spacer
News  (1)  Resources  (1)  Forum  (3)  
 
Negative Oral Contrast AgentsForum -
related threadsInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.MRI Resource Directory:
 - Contrast Agents -
 
Categories of negative oral contrast agents:
Gastrointestinal diamagnetic contrast agents
Gastrointestinal superparamagnetic contrast agents
Perfluorochemicals
Negative oral contrast media are usually based on superparamagnetic particles and act by inducing local field inhomogeneities, which results in shortening of both T1 and T2 relaxation times. Superparamagnetic contrast agents have predominant T2 weighted effects. Biphasic contrast media are agents that have different signal intensities on different sequences, depending on the concentration at which they are used.
Suitable materials for oral contrast agents should have little or no absorption by the stomach or intestines, complete excretion, no motion or susceptibility artifacts, affordability, and uniform marking of the gastrointestinal tract. Benefits of negative oral contrast agents are the reduction of ghosting artifacts caused by the lack of signal. Superparamagnetic iron oxides produce also in low concentrations a noticeable signal loss; but can generate susceptibility artifacts especially in gradient echo sequences. Perfluorochemicals do not dilute in the bowel because they are not miscible with water.
High cost, poor availability, and limited evaluations of side effects are possible disadvantages.
Negative oral contrast agents are used e.g., in MRCP, where the ingestion of 600-900 ml of SPIO cancels out the signal intensity of the lumen (in addition after the injection of a gadolinium-based contrast medium, the enhancement of the inflammatory tissues is clearer seen), and in MR abdominal imaging of Crohn's disease in combination with mannitol.


Contrast Guidance
Blueberry or pineapple juices are useable for examinations of the pancreas (MRCP, upper abdominal imaging) as cheep contrast agents, because of the content of magnetic substances (e.g. manganese). See also Ferristene, Ferumoxsil, Oral Magnetic Particles, Gastrointestinal Imaging.
spacer

• View the DATABASE results for 'Negative Oral Contrast Agents' (7).Open this link in a new window

 
Further Reading:
  Basics:
Components of Oral Contrast Agent for Magnetic Resonance Imaging(.pdf)
   by www.ffcr.or.jp    
MRI Resources 
Education - MRA - Directories - Societies - Portals - Research Labs
 
PRinciples of Echo Shifting using a Train of ObservationsInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(PRESTO) PRESTO is a 3 dimensional ultrafast gradient echo sequence that combines the whole brain coverage with T2* weighted imaging. PRESTO is useful for BOLD and perfusion imaging studies. In combination with parallel imaging techniques, PRESTO provides higher temporal resolution and more coverage compared to traditional multi slice imaging. In addition, the sensitivity to susceptibility artifacts and flow phenomena is reduced, compared with EPI techniques, enabling MRI scans throughout the brain including the skull base.
See also T2 Star.
spacer

• View the DATABASE results for 'PRinciples of Echo Shifting using a Train of Observations' (2).Open this link in a new window

MRI Resources 
Health - Stimulator pool - Implant and Prosthesis pool - General - Universities - Coils
 
previous      61 - 65 (of 85)     next
Result Pages : [1]  [2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17]
 Random Page
 
Share This Page
FacebookTwitterLinkedIn

MR-TIP    
Community   
User
Pass
Forgot your UserID/Password ?  



Your MRI scanner(s) in 5 years should be :
more automated 
much quicker 
quiet 
voice controlled 
iPhone compatible 
as it is right now 

Look
      Ups





MR-TIP.com uses cookies! By browsing MR-TIP.com, you agree to our use of cookies.

Magnetic Resonance - Technology Information Portal
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology-TIP • US-TIP • 
Copyright © 2003 - 2018 SoftWays. All rights reserved. [ 16 January 2019]
Terms of Use | Privacy Policy | Advertising
 [last update: 2018-03-08 05:11:00]