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High Field MRI
 
The principal advantage of MRI at high field is the increase in signal to noise ratio. This can be used to improve anatomic and/or temporal resolution and reduce scan time while preserving image quality. MRI devices for whole body imaging for human use are available up to 3 tesla (3T). Functional MRI (fMRI) and MR spectroscopy (MRS) benefit significantly. In addition, 3T machines have a great utility in applications such as TOF MRA and DTI. Higher field strengths are used for imaging of small parts of the body or scientific animal experiments. Higher contrast may permit reduction of gadolinium doses and, in some cases, earlier detection of disease.
Using high field MRI//MRS, the RF-wavelength and the dimension of the human body complicating the development of MR coils. The absorption of RF power causes heating of the tissue. The energy deposited in the patient's tissues is fourfold higher at 3T than at 1.5T. The specific absorption rate (SAR) induced temperature changes of the human body are the most important safety issue of high field MRI//MRS.
Susceptibility and chemical shift dispersion increase like T1, therefore high field MRI occasionally exhibits imaging artifacts. Most are obvious and easily recognized but some are subtle and mimic diseases. A thorough understanding of these artifacts is important to avoid potential pitfalls. Some imaging techniques or procedures can be utilized to remove or identify artifacts.

See also Diffusion Tensor Imaging.

See also the related poll result: 'In 2010 your scanner will probably work with a field strength of'
Medical-Ultrasound-Imaging.comMagnetic Resonance Guided Focused Ultrasound,  High Intensity Focused Ultrasound
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Further Reading:
  Basics:
Next-generation 7 T scanner ramps the resolution of brain MR imaging
Wednesday, 17 January 2024   by physicsworld.com    
A paired dataset of T1- and T2-weighted MRI at 3 Tesla and 7 Tesla
Thursday, 27 July 2023   by www.nature.com    
CLINICAL WHOLE BODY MRI AT 3.0 T(.pdf)
2001
Musculoskeletal MRI at 3.0 T: Relaxation Times and Image Contrast
Sunday, 1 August 2004   by www.ajronline.org    
  News & More:
How safe is 7T MRI for patients with neurosurgical implants?
Thursday, 17 November 2022   by healthimaging.com    
Impact of Magnetic Field Inhomogeneity on the Quality of Magnetic Resonance Images and Compensation Techniques: A Review
Saturday, 1 October 2022   by www.dovepress.com    
7-T clinical MRI of the shoulder in patients with suspected lesions of the rotator cuff
Friday, 7 February 2020   by eurradiolexp.springeropen.com    
A 100-hour MRI scan captured the most detailed look yet at a whole human brain
Monday, 8 July 2019   by www.sciencenews.or    
T2-Weighted Liver MRI Using the MultiVane Technique at 3T: Comparison with Conventional T2-Weighted MRI
Friday, 16 October 2015   by www.ncbi.nlm.nih.gov    
Ultra-high-field MRI reveals language centres in the brain in much more detail
Tuesday, 28 October 2014   by medicalxpress.com    
Turbo-FLASH Based Arterial Spin Labeled Perfusion MRI at 7 T
Thursday, 20 June 2013   by www.plosone.org    
High-Resolution, Spin-Echo BOLD, and CBF fMRI at 4 and 7 T(.pdf)
October 2002   by otg.downstate.edu    
Vascular Filters of Functional MRI: Spatial Localization Using BOLD and CBV Contrast
MRI Resources 
Nerve Stimulator - Process Analysis - Liver Imaging - Equipment - Calculation - PACS
 
Echo Planar ImagingInfoSheet: - Sequences - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:
 - Sequences -
 
Echo Planar Imaging Timing Diagram (EPI) Echo planar imaging is one of the early magnetic resonance imaging sequences (also known as Intascan), used in applications like diffusion, perfusion, and functional magnetic resonance imaging. Other sequences acquire one k-space line at each phase encoding step. When the echo planar imaging acquisition strategy is used, the complete image is formed from a single data sample (all k-space lines are measured in one repetition time) of a gradient echo or spin echo sequence (see single shot technique) with an acquisition time of about 20 to 100 ms. The pulse sequence timing diagram illustrates an echo planar imaging sequence from spin echo type with eight echo train pulses. (See also Pulse Sequence Timing Diagram, for a description of the components.)
In case of a gradient echo based EPI sequence the initial part is very similar to a standard gradient echo sequence. By periodically fast reversing the readout or frequency encoding gradient, a train of echoes is generated.
EPI requires higher performance from the MRI scanner like much larger gradient amplitudes. The scan time is dependent on the spatial resolution required, the strength of the applied gradient fields and the time the machine needs to ramp the gradients.
In EPI, there is water fat shift in the phase encoding direction due to phase accumulations. To minimize water fat shift (WFS) in the phase direction fat suppression and a wide bandwidth (BW) are selected. On a typical EPI sequence, there is virtually no time at all for the flat top of the gradient waveform. The problem is solved by "ramp sampling" through most of the rise and fall time to improve image resolution.
The benefits of the fast imaging time are not without cost. EPI is relatively demanding on the scanner hardware, in particular on gradient strengths, gradient switching times, and receiver bandwidth. In addition, EPI is extremely sensitive to image artifacts and distortions.
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Further Reading:
  Basics:
New Imaging Method Makes Brain Scans 7 Times Faster
Sunday, 9 January 2011   by www.dailytech.com    
MRI Resources 
Diffusion Weighted Imaging - Stimulator pool - DICOM - Hospitals - Safety pool - Claustrophobia
 
Panorama 0.23T™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.medical.philips.com/main/products/mri/products/panoramafamily/panorama0.23t_rt/features/ From Philips Medical Systems;
the Panorama 0.23 T, providing a new design optimized for patient comfort, faster reconstruction time than before (300 images/second) and new gradient specifications. Philips' Panorama 0.23 T I/T supports MR-guided interventions, resulting in minimally invasive procedures, more targeted surgery, reduced recovery time and shorter hospital stays. Optional OptoGuide functionality enables real-time needle tracking. Philips' Panorama 0.23 TPanorama 0.2 R/T is the first and only open MRI system to enable radiation therapy planning using MR data sets. The Panorama also features the new and consistent Philips User Interface, an essential element of the Vequion clinical IT family of products and services.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Open MRI/C-arm
Head, head-neck, extremity M-L, neck, body/spine S-XL, shoulder, bilateral breast, wrist, TMJ, flex XS-S-M-L-XL-XXL
SYNCHRONIZATION
ECG/peripheral: Optional/optional, respiratory gating
PULSE SEQUENCES
SE, FE, IR, FFE, DEFFE, DESE, TSE, DETSE, Single shot SE, DRIVE, Balanced FFE, MRCP, Fluid Attenuated Inversion Recovery, Turbo FLAIR, IR-TSE, T1-STIR TSE, T2-STIR TSE, Diffusion Imaging, 3D SE, 3D FFE, MTC;; Angiography: CE-ANGIO, MRA 2D, 3D TOF
IMAGING MODES
Single, multislice, volume study, dynamic, SIMEX, multi chunk 3D, multiple stacks
TR
Min. 6.2 msec
TE
Min. 2.8 msec
SINGLE/MULTI SLICE
50 slices/sec
0.4 cm - 40 cm
1280 X 1024
MEASURING MATRIX
Up to 512 x 512
PIXEL INTENSITY
256 gray scale
MAGNET TYPE
Resistive/iron core
Open x 46 cm x infinite (side-first patient entry)
MAGNET WEIGHT
13110 kg
H*W*D
196 x 121 x 176 cm
POWER REQUIREMENTS
400/480 V
COOLING SYSTEM TYPE
Closed loop chilled water (chiller included)
N/A
STRENGTH
19 mT/m
5-GAUSS FRINGE FIELD
2.4 m / 3.7 m
Passive/active
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Further Reading:
  News & More:
Magnetic resonance imaging guided musculoskeletal interventions at 0.23T: Chapter 4. Materials and methods
2002
Searchterm 'functional mri' was also found in the following services: 
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News  (80)  Resources  (24)  Forum  (2)  
 
MAGNETOM 7T
 
www.healthcare.siemens.com/magnetic-resonance-imaging/7t-mri-scanner/magnetom-7t From Siemens Medical Systems;
The MAGNETOM 7T is designed as an open research platform. 7T MRI provides anatomical detail at the submillimiter scale, enhanced contrast mechanisms, outstanding spectroscopy performance, ultra-high resolution functional imaging (fMRI), multinuclear whole-body MRI and functional information.
This ultra high field (UHF) MRI device is a research system and not cleared, approved or licensed in any jurisdiction for patient examinations.
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Compact
7 Tesla
High-performance, ultra high field coils available. Integration and support for coil developments.
CHANNELS (min. / max. configuration)
32, optional 8 channels TX array
Chemical shift imaging, single voxel spectroscopy, multinuclear imaging optional
IMAGING TECHNIQUES
iPAT, mSENSE and GRAPPA (image, k-space), noncontrast angiography, plaque imaging, radial motion compensation
FOV
40 x 40 x 30 cm³ less than 8% nonlinearity
BORE DIAMETER
or W x H
60 cm
TABLE CAPACITY
200 kg
MAGNET WEIGHT (gantry included)
35017 kg
DIMENSION H*W*D (gantry included)
320 x 240 x 317,5 cm
5-GAUSS FRINGE FIELD
7.9 m / 5.6 m
CRYOGEN USE
Zero boil off rate
COOLING SYSTEM
Water
up to 200 T/m/s
MAX. AMPLITUDE
up to 70 mT/m
Up to 3rd order shim coils, user configurable B0 shim ? B0 maps and ROI definition
POWER REQUIREMENTS
2000 Volts, 650A
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Further Reading:
  Basics:
MAGNETOM 7T Product Brochure
   by www.healthcare.siemens.com    
  News & More:
Ultra-high-field MRI may allow earlier diagnosis of Parkinson's disease
Wednesday, 5 March 2014   by www.sciencedaily.com    
Feasibility of Using Ultra-High Field (7 T) MRI for Clinical Surgical Targeting
Thursday, 17 May 2012   by www.plosone.org    
Ultrahigh-Field MRI May Detect Additional Pathology in EAE
Sunday, 20 October 2013   by www.msdiscovery.org    
MRI Resources 
Open Directory Project - Sequences - Abdominal Imaging - Nerve Stimulator - Colonography - Pathology
 
RELAX 0.35T™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
www.isoltech.co.kr/english/product/035t.htm From ISOL Technology
'RELAX is open type MRI system created by making up for the weakness of existing conventional MR systems and applying the strength and the application of the middle to high field MR without uncompromising the image quality.
RELAX offers you a premium mix of form, performance and functionality that are patient and user friendly beyond comparison. - New breed of MRI pursuing - patients comfort'
Device Information and Specification
CLINICAL APPLICATION
Whole body
CONFIGURATION
Open
Head, C-spine, L-spine, TMJ, Knee, Shoulder, General purpose, Phased Array System: 4 digital receiver channels (Up to 12 channels)
SYNCHRONIZATION
ECG/peripheral: Optional/yes, respiratory gating
PULSE SEQUENCES
2D/3D Spin echo, 2D/3D Gradient echo, 2D/3D Fast spin echo, Inversion recovery, 2D/3D Fast gradient echo sequences, FLAIR/STIR, 2D/3D TOF
IMAGING MODES
3D volume imaging (MIP, MPR) MR Angiography package
30 cm
MAGNET TYPE
Permanent
40 cm diameter (patient)
MAGNET WEIGHT
13500 kg
H*W*D
170 x 210 x 130 cm
COOLING SYSTEM TYPE
Water-cooled coil and air-cooled amplifier
STRENGTH
25 - 30 mT/m
5-GAUSS FRINGE FIELD
lower than 2.4 m from the iso-center
Passive and active
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• View the DATABASE results for 'RELAX 0.35T™' (2).Open this link in a new window

MRI Resources 
Jobs pool - Contrast Agents - Safety pool - Manufacturers - Lung Imaging - Databases
 
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