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MRI Resources 
RIS - Absorption and Emission - NMR - Spine MRI - Health - Diffusion Weighted Imaging
 
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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• Related Searches:
    • Gradient Echo Sequence
    • Longitudinal Magnetization
    • Transverse Magnetization
    • Spoiled Gradient Echo Sequence
    • Larmor Frequency
 
Further Reading:
  News & More:
Comparison of New Methods for Magnetic Resonance Imaging of Articular Cartilage(.pdf)
2002
MRI Resources 
Brain MRI - MRI Physics - Corporations - Lung Imaging - Functional MRI - MRI Technician and Technologist Schools
 
Cervical Spine MRI
 
Cervical spine MRI is a suitable tool in the assessment of all cervical spine (vertebrae C1 - C7) segments (computed tomography (CT) images may be unsatisfactory close to the thoracic spine due to shoulder artifacts). The cervical spine is particularly susceptible to degenerative problems caused by the complex anatomy and its large range of motion.
Advantages of magnetic resonance imaging MRI are the high soft tissue contrast (particularly important in diagnostics of the spinal cord), the ability to display the entire spine in sagittal views and the capacity of 3D visualization. Magnetic resonance myelography is a useful supplement to conventional MRI examinations in the investigation of cervical stenosis. Myelographic sequences result in MR images with high contrast that are similar in appearance to conventional myelograms. Additionally, open MRI studies provide the possibility of weight-bearing MRI scan to evaluate structural positional and kinetic changes of the cervical spine.
Indications of cervical spine MRI scans include the assessment of soft disc herniations, suspicion of disc hernia recurrence after operation, cervical spondylosis, osteophytes, joint arthrosis, spinal canal lesions (tumors, multiple sclerosis, etc.), bone diseases (infection, inflammation, tumoral infiltration) and paravertebral spaces.
State-of-the-art phased array spine coils and high performance MRI machines provide high image quality and short scan time. Imaging protocols for the cervical spine includes sagittal T1 weighted and T2 weighted sequences with 3-4 mm slice thickness and axial slices; usually contiguous from C2 through T1. Additionally, T2 fat suppressed and T1 post contrast images are often useful in spine imaging.
See also Lumbar Spine MRI.
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• View the DATABASE results for 'Cervical Spine MRI' (2).Open this link in a new window


• View the NEWS results for 'Cervical Spine MRI' (1).Open this link in a new window.
 
Further Reading:
  News & More:
Pre-Op MRI Predicts Outcome of Cervical Spondylotic Myelopathy
Wednesday, 19 June 2013   by www.doctorslounge.com    
Imaging Technique for Spinal Cord Injury Shows Promise
Sunday, 22 December 2013   by www.wauwatosanow.com    
In Vivo 3-D Cervical Spine Kinematics Demonstrated
Thursday, 19 May 2011   by www.doctorslounge.com    
MRI Images at a 45-Degree Angle Through The Cervic al Neural Forami na:A Technique For Improved Visualization(.pdf)
2006   by www.painphysicianjournal.com    
MRI Resources 
MRI Reimbursement - Spine MRI - Online Books - Implant and Prosthesis pool - IR - Diffusion Weighted Imaging
 
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.


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.
Recently introduced Dixon turbo spin echo (fast spin echo) sequences 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 
PACS - Nerve Stimulator - Safety Training - Health - Brain MRI - Online Books
 
Infinion 1.5T™InfoSheet: - Devices -
Intro, 
Types of Magnets, 
Overview, 
etc.MRI Resource Directory:
 - Devices -
 
From Philips Medical Systems;
www.medical.philips.com/main/products/mri/products/infinion1.5t/features/ Philips Infinion 1.5 T is designed to maximize the efficiency and quality of patient care. Developed with the patient in mind, the Infinion is the shortest and most open 1.5T scanner available. The unique 'ultra short' 1.4 m magnet assures patient comfort and acceptance without compromising image quality and clinical performance.
Device Information and Specification
CLINICAL APPLICATION Whole body
CONFIGURATION Ultra short bore
SURFACE COILS Head, head / neck, integrated C-spine, L/T spine array, small large GP coils, body flex array, torso pelvis array, breast array, endocavitary, shoulder array, lower extremity, hand / wrist, cardiac, PV array
SPECTROSCOPY Yes
SYNCHRONIZATION ECG/peripheral, respiratory gating
PULSE SEQUENCES SE, TSE, SS TSE, EPI, IR, STIR, FLAIR, FFE, TFE, T1 TFE, T2 TFE, Presat, Fatsat, MTC, Diff-opt., Angiography: PCA, MCA, TOF
IMAGING MODES Single slice, single volume, multi slice, multi volume
TR 3.1 msec minimum
TE 0.9 msec minimum
SINGLE/MULTI SLICE 80 images/sec std.; up to320 opt.@256
FOV 0.4 - 56 cm
SLICE THICKNESS 2D: 0.3 mm; 3D: 0.2 mm
DISPLAY MATRIX 1024 x 1024
MEASURING MATRIX 8 x 8 to 1024 x 1024
PIXEL INTENSITY 256 gray scale
SPATIAL RESOLUTION 0.04 mm
MAGNET TYPE Superconducting
BORE DIAMETER
or W x H
60 cm diameter (patient)
MAGNET WEIGHT 4100 kg w/cryogen's
H*W*D 233 (lead fitted) x 198 x 140 cm
POWER REQUIREMENTS 400/480 V
COOLING SYSTEM TYPE Closed loop, chilled water
CRYOGEN USE 0.06 L/hr helium
FIELD STRENGTH 1.5 T
STRENGTH 30 mT/m
5-GAUSS FRINGE FIELD 3.0 m / 5.0 m
SHIMMING Passive/active
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• View the DATABASE results for 'Infinion 1.5T™' (2).Open this link in a new window

MRI Resources 
Artifacts - Contrast Enhanced MRI - MRA - Functional MRI - Cardiovascular Imaging - MRI Centers
 
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 US-TIP.com.
 
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

 
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• 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:
  Basics:
Abdominal MRI at 3.0 T: The Basics Revisited
Wednesday, 20 July 2005   by www.ajronline.org    
Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CT
2000   by www.ncbi.nlm.nih.gov    
MAGNETIC RESONANCE IMAGING OF FOCAL LIVER LESIONS(.pdf)
2002
  News & More:
Nottingham scientists exploit MRI technology to assist in the treatment of IBS
Thursday, 9 January 2014   by www.news-medical.net    
MRI identifies 'hidden' fat that puts adolescents at risk for disease
Tuesday, 27 February 2007   by www.eurekalert.org    
New MR sequence helps radiologists more accurately evaluate abnormalities of the uterus and ovaries
Thursday, 23 April 2009   by www.eurekalert.org    
MRI Resources 
Guidance - Patient Information - Resources - Calculation - MRI Centers - Corporations
 
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