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Result : Searchterm 'Shimming' found in 3 terms [] and 76 definitions []
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Searchterm 'Shimming' was also found in the following services: 
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News  (1)  Resources  (2)  Forum  (9)  
 
FLEXART™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
From Toshiba America Medical Systems Inc.; www3.toshiba.co.jp/medical/products/mr/flex/index.htm FLEXART™ series is a 0.5 T superconducting MRI system that has been designed to meet the expanding role of MRI in today's clinical environment. The system utilizes innovative technologies such as digital RF, high speed actively shielded gradients and optimized RF coils which support a wide range of MRI developments.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Compact
Quadrature, solenoid and multi-channel configurations
SYNCHRONIZATION
ECG/peripheral optional, respiratory gating
PULSE SEQUENCES
SE, FE, IR, FastSE, FastIR, FastFLAIR, Fast STIR, FastFE, FASE, Hybrid EPI, Multi Shot EPI; Angiography: 2D(gate/non-gate)/3D TOF, SORS-STC
IMAGING MODES
Single, multislice, volume study
POWER REQUIREMENTS
380/400/415/440/480 V
COOLING SYSTEM TYPE
Closed-loop water-cooled
STRENGTH
25 mT/m
Passive, active
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MRI Resources 
Universities - Societies - DICOM - Distributors - MRA - Artifacts
 
FORTE 3.0T™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.isoltech.co.kr/english/product/30t.htm From ISOL Technology
'Ultra high field MR system, it's right close to you. FORTE 3.0T is the new standard for the future ultra high field MR system. If you are pushing the limits of your existing clinical MR scanner, the FORTE will surely take you to the next level of diagnostic imaging. FORTE is the core leader of the medical technology in the 21st century. Proving effects of fMRI that cannot be measured with MRI less than 2.0T.'
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Short bore compact
SYNCHRONIZATION
ECG/peripheral: Optional/yes, external trigger, respiratory gating
PULSE SEQUENCES
Spin echo, Gradient echo, Fast spin echo, Inversion recovery, 2D/3D Fast gradient echo sequences FLAIR/STIR, 2D/3D TOF
IMAGING MODES
2D/3D, T1, T2 and Diffusion//Perfusion imaging, MR Angiography package, Advanced EPI package, Multi-nuclei MR Spectroscopy package
FOV
40 cm
128 x 128, 256 x 256, 512 x 512, 1024 x 1024
BORE DIAMETER
or W x H
61 cm without body coil
MAGNET WEIGHT
12000 kg
H*W*D
260 x 220 x 235 cm
COOLING SYSTEM TYPE
Water-cooled coil and air-cooled amplifier
CRYOGEN USE
0.15 L/hr helium
STRENGTH
38 mT/m
5-GAUSS FRINGE FIELD
3.3 m / 5.2 m
Passive and active
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• View the DATABASE results for 'FORTE 3.0T™' (2).Open this link in a new window

MRI Resources 
Examinations - Shielding - Stent - Blood Flow Imaging - Process Analysis - Manufacturers
 
Fast Imaging with Steady PrecessionInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.
 
(TrueFISP) True fast imaging with steady state precession is a coherent technique that uses a fully balanced gradient waveform. The image contrast with TrueFISP is determined by T2*//T1 properties and mostly depending on TR. The speed and relative motion insensitivity of acquisition help to make the technique reliable, even in patients who have difficulty with holding their breath.
Recent advances in gradient hardware have led to a decreased minimum TR. This combined with improved field shimming capabilities and signal to noise ratio, has allowed TrueFISP imaging to become practical for whole-body applications. There's mostly T2* weighting. With the used ultrashort TR-times T1 weighting is almost impossible. One such application is cardiac cine MR with high myocardium-blood contrast. Spatial and temporal resolution can be substantially improved with this technique, but contrast on the basis of the ratio of T2* to T1 is not sufficiently high in soft tissues. By providing T1 contrast, TrueFISP could then document the enhancement effects of T1 shortening contrast agents. These properties are useful for the anatomical delineation of brain tumors and normal structures. With an increase in SNR ratio with minimum TR, TrueFISP could also depict the enhancement effect in myoma uteri. True FSIP is a technique that is well suited for cardiac MR imaging. The imaging time is shorter and the contrast between the blood and myocardium is higher than that of FLASH.

See Steady State Free Precession.
 
Images, Movies, Sliders:
 Cardiac Infarct 4 Chamber Cine 1  Open this link in a new window
    
 
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• View the DATABASE results for 'Fast Imaging with Steady Precession' (3).Open this link in a new window

 
Further Reading:
  Basics:
Accurate T1 Quantification Using a Breath-hold Inversion Recovery TrueFISP Sequence
2003   by rsna2003.rsna.org    
Searchterm 'Shimming' was also found in the following services: 
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News  (1)  Resources  (2)  Forum  (9)  
 
Fat SuppressionForum -
related threads
 
Fat suppression is the process of utilizing specific MRI parameters to remove the deleterious effects of fat from the resulting images , e.g. with STIR, FAT SAT sequences, water selective (PROSET WATS - water only selection, also FATS - fat only selection possible) excitation techniques, or pulse sequences based on the Dixon method.
Spin magnetization can be modulated by using special RF pulses. CHESS or its variations like SPIR, SPAIR (Spectral Selection Attenuated Inversion Recovery) and FAT SAT use frequency selective excitation pulses, which produce fat saturation.
Fat suppression techniques are nearly used in all body parts and belong to every standard MRI protocol of joints like knee, shoulder, hips, etc.
mri safety guidance
Image Guidance
Imaging of, e.g. the foot can induce bad fat suppression with SPIR/FAT SAT due to the asymmetric volume of this body part. The volume of the foot alters the magnetic field to a different degree than the smaller volume of the lower leg affecting the protons there. There is only a small band of tissue where the fat protons are precessing at the frequency expected, resulting in frequency selective fat saturation working only in that area. This can be corrected by volume shimming or creating a more symmetrical volume being imaged with water bags.
Even with their longer scan time and motion sensitivity, STIR (short T1/tau inversion recovery) sequences are often the better choice to suppress fat. STIR images are also preferred because of the decreased sensitivity to field inhomogeneities, permitting larger fields of views when compared to fat suppressed images and the ability to image away from the isocenter.
See also Knee MRI.
Sequences based on Dixon turbo spin echo (fast spin echo) can deliver a significant better fat suppression than conventional TSE/FSE imaging.
 
Images, Movies, Sliders:
 Shoulder Axial T2 FatSat FRFSE  Open this link in a new window
    

Courtesy of  Robert R. Edelman
 MRI Orbita T2 FatSat  Open this link in a new window
    
 Knee MRI Sagittal STIR 001  Open this link in a new window
 MRI - Anatomic Imaging of the Ankle 3  Open this link in a new window
    
SlidersSliders Overview

 
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• View the DATABASE results for 'Fat Suppression' (28).Open this link in a new window

 
Further Reading:
  Basics:
Techniques of Fat Suppression(.pdf)
   by cds.ismrm.org    
  News & More:
Enhanced Fast GRadient Echo 3-Dimensional (efgre3D) or THRIVE
   by www.mri.tju.edu    
Ultrashort echo time (UTE) MRI of the spine in thalassaemia
February 2004   by bjr.birjournals.org    
MRI Resources 
Portals - IR - Process Analysis - Online Books - Brain MRI - Research Labs
 
Field Inhomogeneity ArtifactInfoSheet: - Artifacts - 
Case Studies, 
Reduction Index, 
etc.MRI Resource Directory:
 - Artifacts -
 
Quick Overview
Artifact Information
NAME
Field inhomogeneity
DESCRIPTION
Image distortion signal loss
REASON
HELP
Larger FOV, oversampling
A disturbance of the field homogeneity, because of magnetic material (inside or outside the patient), technical problems or scanning at the edge of the field.
When images were obtained in a progression from the center to the edge of the coil, the homogeneity of the field observed by the imaged volume, changes when the distance from the center of the volume increase. The same problem appears by scanning at a distance from the isocenter in left-right direction or too large field of view.
There are different types of bad image quality, the images are noisy, distorted or the fat suppression doesn't work because of badly set shim currents.
E.g. by using an IR sequence, changes in the T1 recovery rates of the tissues are involved. The inversion time at the center of the imaged volume is appropriate to suppress fat, but at the edge of the coil the same inversion time is sufficient to suppress water. Since the inversion time is not changed, the T1 recovery rates will increase.
mri safety guidance
Image Guidance
Take a smaller imaging volume (and for fat suppression a volume shimming), take care that the imaged region is at the center of the coil and that no magnetic material is inside the imaging volume.
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• View the DATABASE results for 'Field Inhomogeneity Artifact' (3).Open this link in a new window

 
Further Reading:
  Basics:
MRI Artifact Gallery
   by chickscope.beckman.uiuc.edu    
MRI Resources 
Functional MRI - Safety Products - Abdominal Imaging - Databases - Safety pool - Guidance
 
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