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

Out-
      side
 



 
 'Larmor Frequency' 
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 'Larmor Frequency' found in 1 term [] and 26 definitions []
previous     21 - 25 (of 27)     next
Result Pages : [1]  [2 3 4 5 6]
Searchterm 'Larmor Frequency' was also found in the following service: 
spacer
Forum  (1)  
 
Rotating Frame of Reference
 
A 'Rotating Frame of Reference' is a concept to simplify the complex motions of a magnetization vector. The frame of reference rotates about the axis of the external magnetic field B0 (z-axis) at the Larmor frequency of the applied RF magnetic field B1. In this simplified concept the rotating vector B1 appears stationary.
spacer
MRI Resources 
Colonography - Hospitals - MRI Reimbursement - Blood Flow Imaging - Quality Advice - Chemistry
 
Saturation
 
In MR, saturation is a nonequilibrium state with no net magnetization. The same amount of nuclear spins is aligned against and with the magnetic field. Saturation methods like FatSat, SPIR etc., work with a frequency selective saturation pulse for a specific chemical shift applied before the actual sequence starts. This saturation pulse adjusts the magnetization from tissue components to zero. The hydrogen nuclei of fat and water resonate at different frequencies, which makes it possible to excite just the fat with repeatedly applying RF pulses at the Larmor frequency with interpulse times compared to T1. The resulting signal is then destroyed with a gradient pulse (Spoiler Gradient Pulse). Fat is the chemical compound to be saturated at a fat saturation sequence. When the actual sequence follows, (e.g., a spin echo sequence) the unwanted suppressed component will not resonate.

See also Saturation Recovery.
spacer

• View the DATABASE results for 'Saturation' (54).Open this link in a new window

MRI Resources 
Cochlear Implant - Equipment - MRA - Pathology - Spine MRI -
 
Slice SelectionForum -
related threads
 
Exclusive excitation of spins in one slice performed by the coincident combination of a gradient magnetic field and a narrow bandwidth or slice selective RF pulse at a specific Larmor frequency.
spacer

• View the DATABASE results for 'Slice Selection' (8).Open this link in a new window

 
Further Reading:
  Basics:
RARE
Monday, 3 December 2012   by www2.warwick.ac.uk    
  News & More:
Magnetic resonance imaging
   by www.scholarpedia.org    
Searchterm 'Larmor Frequency' was also found in the following service: 
spacer
Forum  (1)  
 
Spectral Line
 
A spectral line is a particular distinct frequency or narrow band of a frequency set. The resonance of this frequency occurs corresponding to a particular chemical shift. Theoretically, the frequency of a pure sine wave displays sharp spectral lines at the point of Larmor frequency. In reality, the spectral lines spread into a blurred peak, caused by field inhomogeneities and spin-spin effect.
spacer

• View the DATABASE results for 'Spectral Line' (21).Open this link in a new window

MRI Resources 
Education - Cochlear Implant - IR - Health - Mass Spectrometry - RIS
 
Spin Density
 
(N) The SI units is moles/m3.
Definition: The concentration of nuclei in tissue processing at the Larmor frequency in a given region; one of the principal determinants of the strength of the NMR signal from the region.
For water, there are about 1.1 x 105 moles of hydrogen per m3, or 0.11 moles of hydrogen/cm3.
The signal intensity measured is related to the square of the xy-magnetization, which in a SE pulse sequence is given by
Mxy = Mxy0(1-exp(-TR/T1)) exp(-TE/T2)
where Mxy0 = Mz0 is proportional to the proton or spin density, and corresponds to the z-magnetization present at zero time of the experiment when it is tilted into the xy-plane.
True spin density is not imaged directly, but must be calculated from signals received with different interpulse times. The spin density contrast can be generated by using a long TR and sampling the data immediately after the RF pulse (with a TE as short as possible).
spacer

• View the DATABASE results for 'Spin Density' (9).Open this link in a new window


• View the NEWS results for 'Spin Density' (1).Open this link in a new window.
 
Further Reading:
  Basics:
Magnetic resonance imaging
   by www.scholarpedia.org    
How Many? A Dictionary of Units of Measurement © Russ Rowlett and the University of North Carolina at Chapel Hill
Wednesday, 21 March 2001   by www.unc.edu    
How does the proton get its spin?
Wednesday, 17 February 2010   by www.physorg.com    
MRI Resources 
MRCP - Knee MRI - MRA - Pathology - Veterinary MRI - MRI Training Courses
 
previous      21 - 25 (of 27)     next
Result Pages : [1]  [2 3 4 5 6]
 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. [ 29 March 2024]
Terms of Use | Privacy Policy | Advertising
 [last update: 2024-02-26 03:41:00]