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

Out-
      side
 



 
 'Susceptibility' 
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 'Susceptibility' found in 3 terms [] and 43 definitions []
previous     21 - 25 (of 46)     next
Result Pages : [1]  [2 3 4 5 6 7 8 9 10]
Searchterm 'Susceptibility' was also found in the following services: 
spacer
News  (3)  Resources  (1)  Forum  (6)  
 
DixonInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
The Dixon technique is a MRI method used for fat suppression and/or fat quantification. The difference in magnetic resonance frequencies between fat and water-bound protons allows the separation of water and fat images based on the chemical shift effect.
This imaging technique is named after Dixon, who published in 1984 the basic idea to use phase differences to calculate water and fat components in postprocessing. Dixon's method relies on acquiring an image when fat and water are 'in phase', and another in 'opposed phase' (out of phase). These images are then added together to get water-only images, and subtracted to get fat-only images. Therefore, this sequence type can deliver up to 4 contrasts in one measurement: in phase, opposed phase, water and fat images. An additional benefit of Dixon imaging is that source images and fat images are also available to the diagnosing physician.
The original two point Dixon sequence (number of points means the number of images acquired at different TE) had limited possibilities to optimize the echo time, spatial resolution, slice thickness, and scan time; but Dixon based fat suppression can be very effective in areas of high magnetic susceptibility, where other techniques fail. This insensitivity to magnetic field inhomogeneity and the possibility of direct image-based water and fat quantification have currently generated high research interests and improvements to the basic method (three point Dixon).
The combination of Dixon with gradient echo sequences allows for example liver imaging with 4 image types in one breath hold. With Dixon TSE/FSE an excellent fat suppression with high resolution can be achieved, particularly useful in imaging of the extremities.
For low bandwidth imaging, chemical shift correction of fat images can be made before recombination with water images to produce images free of chemical shift displacement artifacts. The need to acquire more echoes lengthens the minimum scan time, but the lack of fat saturation pulses extends the maximum slice coverage resulting in comparable scan time.
spacer
 
Further Reading:
  Basics:
Separation of fat and water signal in magnetic resonanace imaging
2011   by www.diva-portal.org    
Direct Water and Fat Determination in Two-Point Dixon Imaging
April 2013   by scholarship.rice.edu    
MRI evaluation of fatty liver in day to day practice: Quantitative and qualitative methods
Wednesday, 3 September 2014   by www.sciencedirect.com    
Measurement of Fat/Water Ratios in Rat Liver Using 3DThree-Point Dixon MRI
2004   by www.civm.duhs.duke.edu    
  News & More:
The utility of texture analysis of kidney MRI for evaluating renal dysfunction with multiclass classification model
Tuesday, 30 August 2022   by www.nature.com    
Liver Imaging Today
Friday, 1 February 2013   by www.healthcare.siemens.it    
mDIXON being developed to simplify and accelerate liver MRI
September 2010   by incenter.medical.philips.com    
MRI Resources 
Online Books - Patient Information - Developers - Spectroscopy pool - Cardiovascular Imaging - Intraoperative MRI
 
Dy-tetraphenyl-porphyrin SulfonateInfoSheet: - Contrast Agents - 
Intro, Overview, 
Characteristics, 
Types of, 
etc.
 
Short name: Dy-TPPS or Ho-TPPS, central moiety: Dy2+Ho2+, contrast effect: negative, high susceptibility
Dy-tetraphenyl-porphyrin sulfonate is a substance under development (preclin.) as a MRI contrast agent with tumor selective uptake for tumor detection and control.
spacer
 
Further Reading:
  News & More:
Dysprosium
   by www.scescape.net    
MRI Resources 
Veterinary MRI - Examinations - Stimulator pool - Software - Breast Implant - Open Directory Project
 
Fast Imaging with Steady State PrecessionInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(FISP) A fast imaging sequence, which attempts to combine the signals observed separately in the FADE sequence, generally sensitive about magnetic susceptibility artifacts and imperfections in the gradient waveforms. Confusingly now often used to refer to a refocused FLASH type sequence.
This sequence is very similar to FLASH, except that the spoiler pulse is eliminated. As a result, any transverse magnetization still present at the time of the next RF pulse is incorporated into the steady state. FISP uses a RF pulse that alternates in sign. Because there is still some remaining transverse magnetization at the time of the RF pulse, a RF pulse of a degree flips the spins less than a degree from the longitudinal axis. With small flip angles, very little longitudinal magnetization is lost and the image contrast becomes almost independent of T1. Using a very short TE (with TR 20-50 ms, flip angle 30-45°) eliminates T2* effects, so that the images become proton density weighted. As the flip angle is increased, the contrast becomes increasingly dependent on T1 and T2*. It is in the domain of large flip angles and short TR that FISP exhibits vastly different contrast to FLASH type sequences. Used for T1 orthopedic imaging, 3D MPR, cardiography and angiography.
spacer

• View the DATABASE results for 'Fast Imaging with Steady State Precession' (5).Open this link in a new window

 
Further Reading:
  Basics:
MRI techniques improve pulmonary embolism detection
Monday, 19 March 2012   by medicalxpress.com    
Searchterm 'Susceptibility' was also found in the following services: 
spacer
News  (3)  Resources  (1)  Forum  (6)  
 
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

 
spacer

• 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 
Cochlear Implant - Mobile MRI - Services and Supplies - General - Spectroscopy - Guidance
 
Ferromagnetic
 
A substance, such as iron, that has a large positive magnetic susceptibility.
spacer

• View the DATABASE results for 'Ferromagnetic' (22).Open this link in a new window

 
Further Reading:
  Basics:
How strong are magnets?
   by my.execpc.com    
  News & More:
Physicists observe an exotic 'multiferroic' state in an atomically thin material
Wednesday, 23 February 2022   by www.sciencedaily.com    
More and More States Adopt Requirements for Ferromagnetic Detectors for MRI Safety
Monday, 19 March 2012   by www.pr.com    
Ultrashort echo time (UTE) MRI of the spine in thalassaemia
February 2004   by bjr.birjournals.org    
MRI Resources 
Nerve Stimulator - Shoulder MRI - Safety Products - Artifacts - MRI Technician and Technologist Jobs - General
 
previous      21 - 25 (of 46)     next
Result Pages : [1]  [2 3 4 5 6 7 8 9 10]
 Random Page
 
Share This Page
FacebookTwitterLinkedIn

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



New acceleration techniques will :
reduce scan times 
cause artifacts 
increase expenses 
be useful if you have a lot of experience 
doesn't do much 
never heard of 

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 • Medical-Ultrasound-Imaging • 
Copyright © 2003 - 2024 SoftWays. All rights reserved. [ 21 November 2024]
Terms of Use | Privacy Policy | Advertising
 [last update: 2024-02-26 03:41:00]