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Result : Searchterm 'Sequences' found in 2 terms [] and 188 definitions []
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Searchterm 'Sequences' was also found in the following services: 
News  (6)  Resources  (8)  Forum  (51)  
SequencesForum -
related threadsInfoSheet: - Sequences - 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
A preselected set of RF (and/or gradient) magnetic field pulses and time spacing between these pulses; used in conjunction with magnetic field gradients and MR signal reception to produce MR images.

See also Pulse Sequence , Interpulse Times and the info sheet.
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• Related Searches:
    • Signal Intensity
    • MRI Scan
    • Proton Density
    • Gradient Echo
    • Spin Echo
Further Reading:
  News & More:
What MRI Sequences Produce the Highest Specific Absorption Rate (SAR), and Is There Something We Should Be Doing to Reduce the SAR During Standard Examinations?
Thursday, 16 April 2015   by    
MRI techniques improve pulmonary embolism detection
Monday, 19 March 2012   by    
Searchterm 'Sequences' was also found in the following services: 
Radiology  (2) Open this link in a new windowUltrasound  (1) Open this link in a new window
Motion Compensation Pulse SequencesInfoSheet: - Sequences - 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
Pulse sequences, designed to be insensitive to flow, e.g. at every even echo, a spin echo sequence is not flow sensitive. Velocity compensation is achieved by using gradients, which are either symmetrical around a 180° pulse and switched on twice as is the case for motion compensated spin echo pulse sequences, or two antisymmetrical gradient lobes without 180° pulse, which is the way to produce a velocity compensated gradient echo pulse sequence.
The signal of the second echo (and all other even echoes) is independent of the velocity of the object. Thus, velocity-based motion effects stemming from the entire voxel or from spins within a voxel (intravoxel incoherent motion) are suppressed with such pulse sequences.
If higher order motion is relevant, as it may be in turbulent jets across valves, acceleration and jerk effects can also be compensated for by the use of appropriate combinations of gradient- and radio frequency pulses.
With the increasingly stronger gradients, echo times in MR systems can be shortened to the point at which effects other than velocity effects hardly ever become relevant.

• View the DATABASE results for 'Motion Compensation Pulse Sequences' (2).Open this link in a new window

Further Reading:
Motion Compensation in MR Imaging
  News & More:
Patient movement during MRI: Additional points to ponder
Tuesday, 5 January 2016   by    
Motion-compensation of Cardiac Perfusion MRI using a Statistical Texture Ensemble(.pdf)
June 2003   by    
MRI Resources 
Artifacts - Implant and Prosthesis pool - Mass Spectrometry - Pregnancy - Diffusion Weighted Imaging - Supplies
Gradient Echo SequenceForum -
related threadsInfoSheet: - Sequences - 
Types of, 
Gradient Echo Sequence Timing Diagram (GRE - sequence) A gradient echo is generated by using a pair of bipolar gradient pulses. In the pulse sequence timing diagram, the basic gradient echo sequence is illustrated. There is no refocusing 180° pulse and the data are sampled during a gradient echo, which is achieved by dephasing the spins with a negatively pulsed gradient before they are rephased by an opposite gradient with opposite polarity to generate the echo.
See also the Pulse Sequence Timing Diagram. There you will find a description of the components.
The excitation pulse is termed the alpha pulse a. It tilts the magnetization by a flip angle a, which is typically between 0° and 90°. With a small flip angle there is a reduction in the value of transverse magnetization that will affect subsequent RF pulses. The flip angle can also be slowly increased during data acquisition (variable flip angle: tilt optimized nonsaturation excitation). The data are not acquired in a steady state, where z-magnetization recovery and destruction by ad-pulses are balanced. However, the z-magnetization is used up by tilting a little more of the remaining z-magnetization into the xy-plane for each acquired imaging line.
Gradient echo imaging is typically accomplished by examining the FID, whereas the read gradient is turned on for localization of the signal in the readout direction. T2* is the characteristic decay time constant associated with the FID. The contrast and signal generated by a gradient echo depend on the size of the longitudinal magnetization and the flip angle. When a = 90° the sequence is identical to the so-called partial saturation or saturation recovery pulse sequence. In standard GRE imaging, this basic pulse sequence is repeated as many times as image lines have to be acquired. Additional gradients or radio frequency pulses are introduced with the aim to spoil to refocus the xy-magnetization at the moment when the spin system is subject to the next a pulse.
As a result of the short repetition time, the z-magnetization cannot fully recover and after a few initial a pulses there is an equilibrium established between z-magnetization recovery and z-magnetization reduction due to the a pulses.
Gradient echoes have a lower SAR, are more sensitive to field inhomogeneities and have a reduced crosstalk, so that a small or no slice gap can be used. In or out of phase imaging depending on the selected TE (and field strength of the magnet) is possible. As the flip angle is decreased, T1 weighting can be maintained by reducing the TR. T2* weighting can be minimized by keeping the TE as short as possible, but pure T2 weighting is not possible. By using a reduced flip angle, some of the magnetization value remains longitudinal (less time needed to achieve full recovery) and for a certain T1 and TR, there exist one flip angle that will give the most signal, known as the "Ernst angle".
Contrast values:
PD weighted: Small flip angle (no T1), long TR (no T1) and short TE (no T2*)
T1 weighted: Large flip angle (70°), short TR (less than 50ms) and short TE
T2* weighted: Small flip angle, some longer TR (100 ms) and long TE (20 ms)

Classification of GRE sequences can be made into four categories:
T1 weighted or incoherent/(RF or gradient) spoiled GRE sequences
T1/T2* weighted or coherent//refocused GRE sequences
T2 weighted contrast enhanced GRE sequences
ultrafast GRE sequences
See also Gradient Recalled Echo Sequence, Spoiled Gradient Echo Sequence, Refocused Gradient Echo Sequence, Ultrafast Gradient Echo Sequence.
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• View the DATABASE results for 'Gradient Echo Sequence' (70).Open this link in a new window

Further Reading:
Enhanced Fast GRadient Echo 3-Dimensional (efgre3D) or THRIVE
Imaging strategies for uncooperative patients
Sunday, 1 January 2017   by    
  News & More:
MRI evaluation of fatty liver in day to day practice: Quantitative and qualitative methods
Wednesday, 3 September 2014   by    
T1rho-prepared balanced gradient echo for rapid 3D T1rho MRI
Monday, 1 September 2008   by    
Searchterm 'Sequences' was also found in the following services: 
News  (6)  Resources  (8)  Forum  (51)  
Knee MRI
Knee MRI, with its high soft tissue contrast is one of the main imaging tools to depict knee joint pathology. MRI allows accurate imaging of intra-articular structures such as ligaments, cartilage, menisci, bone marrow, synovium, and adjacent soft tissue.
Knee exams require a dedicated extremity coil, providing a homogenous imaging volume and high SNR to ensure best signal coverage. A complete knee MR examination includes for example sagittal and coronal T1 weighted, and proton density weighted pulse sequences +/- fat saturation, or STIR sequences. For high spatial resolution, maximal 4 mm thick slices with at least an in plane resolution of 0.75 mm and small gap are recommended. To depict the anterior cruciate ligament clearly, the sagittal plane has to be rotated 10 - 20° externally (parallel to the medial border of the femoral condyle). Retropatellar cartilage can bee seen for example in axial T2 weighted gradient echo sequences with Fatsat. However, the choice of the pulse sequences is depended of the diagnostic question, the used scanner, and preference of the operator.
Diagnostic quality in knee imaging is possible with field strengths ranging from 0.2 to 3T. With low field strengths more signal averages must be measured, resulting in increased scan times to provide equivalent quality as high field strengths.
More diagnostic information of meniscal tears and chondral defects can be obtained by direct magnetic resonance arthrography, which is done by introducing a dilute solution of gadolinium in saline (1:1000) into the joint capsule. The knee is then scanned in all three planes using T1W sequences with fat suppression. For indirect arthrography, the contrast is given i.v. and similar scans are started 20 min. after injection and exercise of the knee.
Frequent indications of MRI scans in musculoskeletal knee diseases are:
e.g., meniscal degeneration and tears, ligament injuries, osteochondral fractures, osteochondritis dissecans, avascular bone necrosis and rheumatoid arthritis.
See also Imaging of the Extremities and STIR.
Images, Movies, Sliders:
 Sagittal Knee MRI Images T1 Weighted  Open this link in a new window

 Anatomic MRI of the Knee 2  Open this link in a new window
SlidersSliders Overview

 Knee MRI Coronal Pd Spir 001  Open this link in a new window
 Sagittal Knee MRI Images STIR  Open this link in a new window

 Axial Knee MRI Images T2 Weighted  Open this link in a new window
 Anatomic MRI of the Knee 1  Open this link in a new window
SlidersSliders Overview

Radiology-tip.comArthrography,  Bone Scintigraphy
Radiology-tip.comMusculoskeletal and Joint Ultrasound,  Sonography

• View the DATABASE results for 'Knee MRI' (4).Open this link in a new window

• View the NEWS results for 'Knee MRI' (4).Open this link in a new window.
Further Reading:
Musculoskeletal MRI at 3.0 T: Relaxation Times and Image Contrast
Sunday, 1 August 2004   by    
Knee, Anterior Cruciate Ligament Injuries (MRI)
Tuesday, 28 March 2006   by    
Empirical evaluation of the inter-relationship of articular elements involved in the pathoanatomy of knee osteoarthritis using Magnetic Resonance Imaging
Friday, 30 October 2009   by    
  News & More:
Researcher uses MRI to measure joint's geometry and role in severe knee injury
Tuesday, 23 September 2014   by    
Abnormalities on MRI predict knee replacement
Monday, 9 March 2015   by    
Financial Interest May Motivate Higher Knee MRI Referral
Wednesday, 4 December 2013   by    
Study: MRI scans of knees can be used for biometric identification
Wednesday, 23 January 2013   by    
Searchterm 'Sequences' was also found in the following services: 
Radiology  (2) Open this link in a new windowUltrasound  (1) Open this link in a new window
Abdominal ImagingMRI Resource Directory:
 - Abdominal Imaging -
General MRI of the abdomen can consist of T1 or T2 weighted spin echo, fast spin echo (FSE, TSE) or gradient echo sequences with fat suppression and contrast enhanced MRI techniques. The examined organs include liver, pancreas, spleen, kidneys, adrenals as well as parts of the stomach and intestine (see also gastrointestinal imaging). Respiratory compensation and breath hold imaging is mandatory for a good image quality.
T1 weighted sequences are more sensitive for lesion detection than T2 weighted sequences at 0.5 T, while higher field strengths (greater than 1.0 T), T2 weighted and spoiled gradient echo sequences are used for focal lesion detection. Gradient echo in phase T1 breath hold can be performed as a dynamic series with the ability to visualize the blood distribution. Phases of contrast enhancement include the capillary or arterial dominant phase for demonstrating hypervascular lesions, in liver imaging the portal venous phase demonstrates the maximum difference between the liver and hypovascular lesions, while the equilibrium phase demonstrates interstitial disbursement for edematous and malignant tissues.
Out of phase gradient echo imaging for the abdomen is a lipid-type tissue sensitive sequence and is useful for the visualization of focal hepatic lesions, fatty liver (see also Dixon), hemochromatosis, adrenal lesions and renal masses. The standards for abdominal MRI vary according to clinical sites based on sequence availability and MRI equipment. Specific abdominal imaging coils and liver-specific contrast agents targeted to the healthy liver tissue improve the detection and localization of lesions.
See also Hepatobiliary Contrast Agents, Reticuloendothelial Contrast Agents, and Oral Contrast Agents.

For Ultrasound Imaging (USI) see Abdominal Ultrasound at
Images, Movies, Sliders:
 MR Colonography Gadolinium per Rectum  Open this link in a new window

Courtesy of  Robert R. Edelman
 Anatomic Imaging of the Liver  Open this link in a new window

 CE MRA of the Aorta  Open this link in a new window
SlidersSliders Overview


• View the DATABASE results for 'Abdominal Imaging' (11).Open this link in a new window

• View the NEWS results for 'Abdominal Imaging' (3).Open this link in a new window.
Further Reading:
Abdominal MRI at 3.0 T: The Basics Revisited
Wednesday, 20 July 2005   by    
Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CT
2000   by    
  News & More:
RSI-MRI imaging technology can effectively differentiate aggressive prostate cancer
Thursday, 2 June 2016   by    
Computer-aided detection and diagnosis for prostate cancer based on mono and multi-parametric MRI: A review - Abstract
Tuesday, 28 April 2015   by    
MRI for differentiating ovarian endometrioid adenocarcinoma from high-grade serous adenocarcinoma
Wednesday, 29 April 2015   by    
MRI identifies 'hidden' fat that puts adolescents at risk for disease
Tuesday, 27 February 2007   by    
Nottingham scientists exploit MRI technology to assist in the treatment of IBS
Thursday, 9 January 2014   by    
New MR sequence helps radiologists more accurately evaluate abnormalities of the uterus and ovaries
Thursday, 23 April 2009   by    
MRI Resources 
Bioinformatics - RIS - MRI Reimbursement - Movies - Image Quality - MR Guided Interventions
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