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

Out-
      side
 



 
 MRI Database 
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
previous     86 - 90 (of 98)     next 
Fa-Fa   Fa-Fa   Fa-Fa   Fa-Fa   Fa-Fe   Fe-Fe   Fe-Fe   Fe-Fe   Fe-Fi   Fi-Fi   Fi-Fi   Fi-Fl   FL-Fl   Fl-Fl   Fl-Fl   Fo-Fo   FO-Fr   Fr-Fr     Fr-Fu   Fu-Fu   
MRI Resources 
Breast Implant - Anatomy - MRI Technician and Technologist Schools - Safety pool - Research Labs - Equipment
 
Fractional Nex Imaging
 
Fractional Nex imaging (GE Healthcare term for imaging with a Nex value less than 1) benefits from the conjugate symmetry of the k-space to reduce the number of phase encoding acquisitions. With fractional Nex imaging (similar to partial Fourier or Half Scan), just over half of the data are acquired and the data from the lower part of k-space are used to fill the upper part, without sampling the upper part. Fractional Nex imaging sequences use a number of excitations values between 0.5 and 1. These values are a bit misleading, because the number of phase encoding steps is reduced, and not the NEX.
Fractional Nex imaging reduces the scan time considerable, by preserving the same contrast between the tissues. The effect by acquiring fewer data points is that the signal to noise ratio decreases.

See also acronyms for 'partial averaging//fractional Nex imaging' from different manufacturers.
spacer
 
Further Reading:
  Basics:
Method and apparatus for subterranean formation flow imaging
   by www.google.com    
CHAPTER-12
   by www.cis.rit.edu    
  News & More:
A Practical Guide to Cardiovascular MRI
   by www.gehealthcare.com    
Free Induction Decay
 
(FID) A free induction decay curve is generated as excited nuclei relax. The amplitude of the FID signal becomes smaller over time as net magnetization returns to equilibrium. If transverse magnetization of the spins is produced, e.g. by a 90° pulse, a transient MR signal will result that will decay toward zero with a characteristic time constant T2 (or T2*); this decaying signal is the free induction decay.
The signal peaks of the echoes fall onto this T2 decay curve, while at each echo the signals arise and decay with T2*. The typical T2 relaxation times being of the order of 5-200 ms in the human body. The first part of the FID is not observable (named the 'receiver dead time') caused by residual effects of the powerful exciting radio frequency pulse on the electronics of the receiver.
spacer

• View the DATABASE results for 'Free Induction Decay' (8).Open this link in a new window

 
Further Reading:
  Basics:
Free induction decay
   by en.wikipedia.org    
  News & More:
Magnetic resonance imaging
   by www.scholarpedia.org    
MRI Resources 
Pathology - Case Studies - NMR - Used and Refurbished MRI Equipment - Devices - Breast Implant
 
Free Pool
 
Only the moveable (free) spins have a defined Larmor frequency and are visible in the image.
spacer
 
Further Reading:
  News & More:
New Imaging Technique Reveals Structural Changes In Tourette's
Saturday, 16 May 2009   by www.sciencedaily.com    
FrequencyForum -
there are related threads
 
(F) The number of repetitions of a periodic process per unit time. It is related to angular frequency, w, by f = w/2p. In electromagnetic radiation, it is usually expressed in units of Hertz (Hz), where 1 Hz = 1 cycle per second.
spacer

• View the NEWS results for 'Frequency' (3).Open this link in a new window.

• View the DATABASE results for 'Frequency' (251).Open this link in a new window

 
Further Reading:
  News & More:
Safety and reliability of Radio Frequency Identification Devices in Magnetic Resonance Imaging and Computed Tomography
Thursday, 4 February 2010   by 7thspace.com    
Improved shim method based on the minimization of the maximum off-resonance frequency for balanced SSFP
Monday, 1 June 2009   by www.ncbi.nlm.nih.gov    
Frequency Encoding
 
Encoding the distribution of sources of MR signals along a direction in space with different frequencies. In general, it is necessary to acquire a set of signals with a suitable set of different frequencies in order to reconstruct the distribution of the sources along the encoded direction. In the absence of other position encoding, the Fourier transformation of the resulting signal is a one-dimensional projection profile of the object.
spacer

• View the DATABASE results for 'Frequency Encoding' (31).Open this link in a new window

 
Further Reading:
  Basics:
Measuring T1 and T2 Relaxation - Introductory NMR & MRI from Magritek
   by www.azom.com    
Aliasing or wrap around artifacts
Thursday, 31 March 2011   by de.slideshare.net    
MRI Resources 
Shoulder MRI - Cochlear Implant - Services and Supplies - Collections - Diffusion Weighted Imaging - Contrast Enhanced MRI
 
previous       86 - 90 (of 98)      next 
Fa-Fa   Fa-Fa   Fa-Fa   Fa-Fa   Fa-Fe   Fe-Fe   Fe-Fe   Fe-Fe   Fe-Fi   Fi-Fi   Fi-Fi   Fi-Fl   FL-Fl   Fl-Fl   Fl-Fl   Fo-Fo   FO-Fr    Fr-Fr    Fr-Fu   Fu-Fu   
 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]