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

Out-
      side
 



 
 'Number of Echoes' 
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 'Number of Echoes' found in 1 term [] and 3 definitions [], (+ 4 Boolean[] results
1 - 5 (of 8)     next
Result Pages : [1]  [2]
MRI Resources 
Mobile MRI - Contrast Enhanced MRI - Sequences - Safety Training - Movies - Collections
 
Number of EchoesInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
The number of series of 180° RF rephasing pulses and their corresponding echoes for a fast or turbo spin echo pulse sequence is named echo train length (ETL) or turbo spin echo turbo factor (TSE TF).
spacer
 
• Share the entry 'Number of Echoes':  Facebook  Twitter  LinkedIn  
MRI Resources 
Libraries - Guidance - Jobs pool - Brain MRI - Case Studies - MRI Technician and Technologist Career
 
Double Contrast SequenceInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
This sequence type is a TSE counterpart to double echo sequences. To keep the echo train as short as possible, only echoes for PD and T2 weighted images, where the phase encoding gradient has a small amplitude, are measured separately. The echoes that determine resolution are used in both raw data matrices. This reduces the number of echoes required. Also the SAR drops and more slices can be acquired in the same repetition time.
spacer
 
Further Reading:
  Basics:
BASIC PRINCIPLES OF MR IMAGING
   by spinwarp.ucsd.edu    
MRI Resources 
MRI Reimbursement - Sequences - Contrast Enhanced MRI - Claustrophobia - Stent - Jobs pool
 
EchoForum -
related threads
 
In MRI, an echo is the emission of energy in form of an electromagnetic resonance signal of a nuclei after its excitation. At this point spins are back in phase again and the signal is measured. The desired number of echoes is selectable. Often until eight echoes are permissible for 2D or 3D scans using spin echo, inversion recovery or MIX techniques. Two echoes are permissible for all other techniques. A multi echo imaging sequence is needed for simultaneous measurement of T2 and density weighted images.
spacer

• View the DATABASE results for 'Echo' (305).Open this link in a new window


• View the NEWS results for 'Echo' (4).Open this link in a new window.
 
Further Reading:
  News & More:
Ultrashort echo time (UTE) MRI of the spine in thalassaemia
February 2004   by bjr.birjournals.org    
UCLA chemists use MRI to peek at temperatures of gases inside catalytic reactors
Thursday, 24 October 2013   by esciencenews.com    
MRI Resources 
Mobile MRI Rental - Most Wanted - Artifacts - Pregnancy - Mobile MRI - Claustrophobia
 
Turbo Spin Echo Turbo Factor
 
(TSE TF) The turbo factor is the number of echoes acquired after each excitation. This is a measure of the scan time acceleration, e.g. at turbo factor 3 the scan time is 3 times faster as a SE sequence with comparable parameters. In combination with profile order and effective echo time the TSE turbo factor controls the echo spacing.

See also Scan Time and Echo Spacing.
spacer

• View the DATABASE results for 'Turbo Spin Echo Turbo Factor' (5).Open this link in a new window

 
Further Reading:
  News & More:
Comparison of Fast Spin-Echo Versus Conventional Spin-Echo MRI forEvaluating Meniscal Tears
June 2005   by www.ajronline.org    
MRI Resources 
MR Guided Interventions - Case Studies - Stent - Developers - Open Directory Project - MRI Accidents
 
Sensitivity EncodingInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(SENSE) A MRI technique for relevant scan time reduction. The spatial information related to the coils of a receiver array are utilized for reducing conventional Fourier encoding. In principle, SENSE can be applied to any imaging sequence and k-space trajectories. However, it is particularly feasible for Cartesian sampling schemes. In 2D Fourier imaging with common Cartesian sampling of k-space sensitivity encoding by means of a receiver array enables to reduce the number of Fourier encoding steps.
SENSE reconstruction without artifacts relies on accurate knowledge of the individual coil sensitivities. For sensitivity assessment, low-resolution, fully Fourier-encoded reference images are required, obtained with each array element and with a body coil.
The major negative point of parallel imaging techniques is that they diminish SNR in proportion to the numbers of reduction factors. R is the factor by which the number of k-space samples is reduced. In standard Fourier imaging reducing the sampling density results in the reduction of the FOV, causing aliasing. In fact, SENSE reconstruction in the Cartesian case is efficiently performed by first creating one such aliased image for each array element using discrete Fourier transformation (DFT).
The next step then is to create a full-FOV image from the set of intermediate images. To achieve this one must undo the signal superposition underlying the fold-over effect. That is, for each pixel in the reduced FOV the signal contributions from a number of positions in the full FOV need to be separated. These positions form a Cartesian grid corresponding to the size of the reduced FOV.
The advantages are especially true for contrast-enhanced MR imaging such as dynamic liver MRI (liver imaging) , 3 dimensional magnetic resonance angiography (3D MRA), and magnetic resonance cholangiopancreaticography (MRCP).
The excellent scan speed of SENSE allows for acquisition of two separate sets of hepatic MR images within the time regarded as the hepatic arterial-phase (double arterial-phase technique) as well as that of multidetector CT.
SENSE can also increase the time efficiency of spatial signal encoding in 3D MRA. With SENSE, even ultrafast (sub second) 4D MRA can be realized.
For MRCP acquisition, high-resolution 3D MRCP images can be constantly provided by SENSE. This is because SENSE resolves the presence of the severe motion artifacts due to longer acquisition time. Longer acquisition time, which results in diminishing image quality, is the greatest problem for 3D MRCP imaging.
In addition, SENSE reduces the train of gradient echoes in combination with a faster k-space traversal per unit time, thereby dramatically improving the image quality of single shot echo planar imaging (i.e. T2 weighted, diffusion weighted imaging).
spacer

• View the DATABASE results for 'Sensitivity Encoding' (12).Open this link in a new window

 
Further Reading:
  News & More:
Image Characteristics and Quality
   by www.sprawls.org    
MRI Resources 
Claustrophobia - Societies - Collections - Stimulator pool - Guidance - Online Books
 
     1 - 5 (of 8)     next
Result Pages : [1]  [2]
 Random Page
 
Share This Page
FacebookTwitterLinkedIn

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



Personalized protocols (age, gender, body habitus, etc.) lead to :
more automated planning 
improved patient comfort 
better diagnostics 
optimized image quality 
nothing 

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. [ 28 March 2024]
Terms of Use | Privacy Policy | Advertising
 [last update: 2024-02-26 03:41:00]