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Staircase ArtifactInfoSheet: - Artifacts -
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Staircase
DESCRIPTION
Staircase like nuance
REASON
Slices too thick, no overlapping
HELP
Overlapping slices
Staircase artifacts might be seen in projection of the slice thickness in case of MIP or MPR reconstructions.
mri safety guidance
Image Guidance
Use overlapping slices to reduce this artifact by changing the slice gap to a negative value. In most cases, a negative value of 20-30% is sufficient.
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State Food and Drug Administration
 
eng.sfda.gov.cn/eng (SFDA) The State Food and Drug Administration of the People's Republic of China was founded in November 2003 and is directly under the State Council. The State Food and Drug Administration is in charge of comprehensive supervision on the safety management of food, health food and cosmetics and is the competent authority of drug regulation. For drug or medical device registration please see the SFDA's Regulatory Guide.
The agency is China's equivalent of the US Food and Drug Administration.
Contact Information
MAIL
State Food and Drug Administration
A38, Beilishi Road
Beijing 100810
P.R. China
FAX
86-010-68310909
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• View the DATABASE results for 'State Food and Drug Administration' (2).Open this link in a new window

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Diffusion Weighted Imaging - MR Myelography - Databases - Liver Imaging - MRA - MRI Technician and Technologist Jobs
 
Steady State Coherent
 
A state of spins, which leads to an equilibrium magnetization for the longitudinal and transverse magnetization, or, when the magnetization at, or after, each RF pulse is the same as in the previous pulse.
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Steady State Free PrecessionInfoSheet: - Sequences -
Intro, Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(SFP or SSFP) Steady state free precession is any field or gradient echo sequence in which a non-zero steady state develops for both components of magnetization (transverse and longitudinal) and also a condition where the TR is shorter than the T1 and T2 times of the tissue. If the RF pulses are close enough together, the MR signal will never completely decay, implying that the spins in the transverse plane never completely dephase. The flip angle and the TR maintain the steady state. The flip angle should be 60-90° if the TR is 100 ms, if the TR is less than 100 ms, then the flip angle for steady state should be 45-60°.
Steady state free precession is also a method of MR excitation in which strings of RF pulses are applied rapidly and repeatedly with interpulse intervals short compared to both T1 and T2. Alternating the phases of the RF pulses by 180° can be useful. The signal reforms as an echo immediately before each RF pulse; immediately after the RF pulse there is additional signal from the FID produced by the pulse.
The strength of the FID will depend on the time between pulses (TR), the tissue and the flip angle of the pulse; the strength of the echo will additionally depend on the T2 of the tissue. With the use of appropriate dephasing gradients, the signal can be observed as a frequency-encoded gradient echo either shortly before the RF pulse or after it; the signal immediately before the RF pulse will be more highly T2 weighted. The signal immediately after the RF pulse (in a rapid series of RF pulses) will depend on T2 as well as T1, unless measures are taken to destroy signal refocusing and prevent the development of steady state free precession.
To avoid setting up a state of SSFP when using rapidly repeated excitation RF pulses, it may be necessary to spoil the phase coherence between excitations, e.g. with varying phase shifts or timing of the exciting RF pulses or varying spoiler gradient pulses between the excitations.
Steady state free precession imaging methods are quite sensitive to the resonant frequency of the material. Fluctuating equilibrium MR (see also FIESTA and DRIVE)and linear combination SSFP actually use this sensitivity for fat suppression. Fat saturated SSFP (FS-SSFP) use a more complex fat suppression scheme than FEMR or LCSSFP, but has a 40% lower scan time.
A new family of steady state free precession sequences use a balanced gradient, a gradient waveform, which will act on any stationary spin on resonance between 2 consecutive RF pulses and return it to the same phase it had before the gradients were applied.
This sequences include, e.g. Balanced Fast Field Echo - bFFE, Balanced Turbo Field Echo - bTFE, Fast Imaging with Steady Precession - TrueFISP and Balanced SARGE - BASG.

See also FIESTA.
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• View the DATABASE results for 'Steady State Free Precession' (20).Open this link in a new window

 
Further Reading:
  News & More:
Comparison of New Methods for Magnetic Resonance Imaging of Articular Cartilage(.pdf)
2002
Steady State Free Precession SequenceInfoSheet: - Sequences -
Intro, Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
(SFP or SSFP) Steady state free precession is any field or gradient echo sequence where the TR is shorter than the T1 and T2 times of the tissue.
The flip angle and the TR maintain the steady state. The flip angle should be 60-90° if the TR is 100 ms, if the TR is less than 100 ms, than the choice of the flip angle for steady state is 45-60°. The T1 weighting is controlled by TR and flip, the T2 weighting increases with the TE. Common TR is between 20 - 50 msec.
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Further Reading:
  News & More:
Generic Eddy Current Compensation for Rapid Magnetic Resonance Imaging(.pdf)
   by www.switt.ch    
Cutting Edge Imaging of THE Spine
February 2007   by www.pubmedcentral.nih.gov    
MRI Resources 
PACS - Stent - MRI Physics - Equipment - MRI Technician and Technologist Career - Image Quality
 
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