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Spin Echo SequenceInfoSheet: - Sequences - 
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Spin Echo Timing Diagram (SE) The most common pulse sequence used in MR imaging is based of the detection of a spin or Hahn echo. It uses 90 radio frequency pulses to excite the magnetization and one or more 180 pulses to refocus the spins to generate signal echoes named spin echoes (SE).
In the pulse sequence timing diagram, the simplest form of a spin echo sequence is illustrated.
The 90 excitation pulse rotates the longitudinal magnetization (Mz) into the xy-plane and the dephasing of the transverse magnetization (Mxy) starts.
The following application of a 180 refocusing pulse (rotates the magnetization in the x-plane) generates signal echoes. The purpose of the 180 pulse is to rephase the spins, causing them to regain coherence and thereby to recover transverse magnetization, producing a spin echo.
The recovery of the z-magnetization occurs with the T1 relaxation time and typically at a much slower rate than the T2-decay, because in general T1 is greater than T2 for living tissues and is in the range of 1002000 ms.
The SE pulse sequence was devised in the early days of NMR days by Carr and Purcell and exists now in many forms: the multi echo pulse sequence using single or multislice acquisition, the fast spin echo (FSE/TSE) pulse sequence, echo planar imaging (EPI) pulse sequence and the gradient and spin echo (GRASE) pulse sequence;; all are basically spin echo sequences.
In the simplest form of SE imaging, the pulse sequence has to be repeated as many times as the image has lines.
Contrast values:
PD weighted: Short TE (20 ms) and long TR.
T1 weighted: Short TE (10-20 ms) and short TR (300-600 ms)
T2 weighted: Long TE (greater than 60 ms) and long TR (greater than 1600 ms)
With spin echo imaging no T2* occurs, caused by the 180 refocusing pulse. For this reason, spin echo sequences are more robust against e.g., susceptibility artifacts than gradient echo sequences.
See also Pulse Sequence Timing Diagram to find a description of the components.
 
Images, Movies, Sliders:
 Shoulder Coronal T1 SE  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 Shoulder Axial T1 SE  Open this link in a new window
 MRI Orbita T1  Open this link in a new window
    
 
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Further Reading:
  Basics:
Fast Spin Echo(.pdf)
Tuesday, 24 January 2006   by www.81bones.net    
Magnetic resonance imaging
   by www.scholarpedia.org    
FUNDAMENTALS OF MRI: Part I
   by www.e-radiography.net    
  News & More:
New MR sequence helps radiologists more accurately evaluate abnormalities of the uterus and ovaries
Thursday, 23 April 2009   by www.eurekalert.org    
MRI techniques improve pulmonary embolism detection
Monday, 19 March 2012   by medicalxpress.com    
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Spin Echo Sequence for Spatial LocalizationInfoSheet: - Sequences - 
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(DEPTH) A sequence with multiple RF pulses to enable acquiring data from only selected regions.
See Depth Pulses, Volume Selective Excitation, Depth Resolved Spectroscopy.
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Fast Spin EchoForum -
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Fast Spin Echo Diagram

(FSE) In the pulse sequence timing diagram, a fast spin echo sequence with an echo train length of 3 is illustrated. This sequence is characterized by a series of rapidly applied 180 rephasing pulses and multiple echoes, changing the phase encoding gradient for each echo.
The echo time TE may vary from echo to echo in the echo train. The echoes in the center of the K-space (in the case of linear k-space acquisition) mainly produce the type of image contrast, whereas the periphery of K-space determines the spatial resolution. For example, in the middle of K-space the late echoes of T2 weighted images are encoded. T1 or PD contrast is produced from the early echoes.
The benefit of this technique is that the scan duration with, e.g. a turbo spin echo turbo factor / echo train length of 9, is one ninth of the time. In T1 weighted and proton density weighted sequences, there is a limit to how large the ETL can be (e.g. a usual ETL for T1 weighted images is between 3 and 7). The use of large echo train lengths with short TE results in blurring and loss of contrast. For this reason, T2 weighted imaging profits most from this technique.
In T2 weighted FSE images, both water and fat are hyperintense. This is because the succession of 180 RF pulses reduces the spin spin interactions in fat and increases its T2 decay time. Fast spin echo (FSE) sequences have replaced conventional T2 weighted spin echo sequences for most clinical applications. Fast spin echo allows reduced acquisition times and enables T2 weighted breath hold imaging, e.g. for applications in the upper abdomen.
In case of the acquisition of 2 echoes this type of a sequence is named double fast spin echo / dual echo sequence, the first echo is usually density and the second echo is T2 weighted image. Fast spin echo images are more T2 weighted, which makes it difficult to obtain true proton density weighted images. For dual echo imaging with density weighting, the TR should be kept between 2000 - 2400 msec with a short ETL (e.g., 4).
Other terms for this technique are:
Turbo Spin Echo
Rapid Imaging Spin Echo,
Rapid Spin Echo,
Rapid Acquisition Spin Echo,
Rapid Acquisition with Refocused Echoes

 
Images, Movies, Sliders:
 Lumbar Spine T2 FSE Sagittal  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 MRI - Anatomic Imaging of the Foot  Open this link in a new window
    
SlidersSliders Overview

 Lumbar Spine T2 FSE Axial  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 
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• View the DATABASE results for 'Fast Spin Echo' (31).Open this link in a new window

 
Further Reading:
  Basics:
MYELIN-SELECTIVE MRI: PULSE SEQUENCE DESIGN AND OPTIMIZATION
   by www.imaging.robarts.ca    
Advances in Magnetic Resonance Neuroimaging
Friday, 27 February 2009   by www.ncbi.nlm.nih.gov    
  News & More:
New MR sequence helps radiologists more accurately evaluate abnormalities of the uterus and ovaries
Thursday, 23 April 2009   by www.eurekalert.org    
Spin echoes, CPMG and T2 relaxation - Introductory NMR & MRI from Magritek
2013   by www.azom.com    
Scanning the Abdomen
   by www.mrprotocols.com    
Searchterm 'Spin Echo Sequence' was also found in the following service: 
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Gradient and Spin EchoInfoSheet: - Sequences - 
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(GRASE) A hybrid sequence with a combination of gradient and spin echo sequences. If multiple image lines are obtained during a single echo, the imaging pulse sequence type is a GRASE sequence.
See Gradient Echo Sequence and Spin Echo Sequence.
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• View the DATABASE results for 'Gradient and Spin Echo' (3).Open this link in a new window

 
Further Reading:
  Basics:
GRASE (Gradient- and Spin-Echo) MR of the Brain
   by www.ajnr.org    
  News & More:
Sequence for Philips(.pdf)
   by www.droid.cuhk.edu.hk    
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Black Blood MRAForum -
related threadsInfoSheet: - Sequences - 
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 - Cardiovascular Imaging -
 
With this magnetic resonance angiography technique flowing blood appears dark.
MR black blood techniques have been developed for cardiovascular imaging to improve segmentation of myocardium from the blood pool. Black blood MRA techniques decrease the signal from blood with reference to the myocardium and make it easier to perform cardiac chamber segmentation.
ECG gated spin echo sequences with presaturation pulses for magnetization preparation will show strong intravascular signal loss due to flow effects when appropriate imaging conditions including spatial presaturation are used. The sequence use the flow void effect as blood passes rapidly through the selected slice.
For dark blood preparation, a pair of nonselective and selective 180 inversion pulses are used, followed by a long inversion time to null signal from inflowing blood. A second selective inversion pulse can also be applied with short inversion time to null the fat signal. These in cardiac imaging used black blood techniques are referred to as double inversion recovery T1 measurement turbo spin echo or fast spin echo, and double-inversion recovery STIR.
 
Images, Movies, Sliders:
 Normal Dual Inversion Fast Spin-echo  Open this link in a new window
      

Courtesy of  Robert R. Edelman

 
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