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MRI of the lumbar spine, with its multiplanar 3 dimensional imaging capability, is currently the preferred modality for establishing a diagnosis. MRI scans and magnetic resonance myelography have many advantages compared with computed tomography and/or X-ray myelography in evaluating the lumbar spine. MR imaging scans large areas of the spine without ionizing radiation, is noninvasive, not affected by bone artifacts, provides vascular imaging capability, and makes use of safer contrast agents ( gadolinium chelate).
Due to the high level of tissue contrast resolution, nerves and discs are clearly visible. MRI is excellent for detecting degenerative disease in the spine. Lumbar spine MRI accurately shows disc disease (prolapsed disc or slipped disc), the level at which disc disease occurs, and if a disc is compressing spinal nerves. Lumbar spine MRI depicts soft tissues, including the cauda equina, spinal cord, ligaments, epidural fat, subarachnoid space, and intervertebral discs. Loss of epidural fat on T1 weighted images, loss of cerebrospinal fluid signal around the dural sac on T2 weighted images and degenerative disc disease are common features of lumbar stenosis.
Common indications for MRI of the lumbar spine:
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Neurologic deficits, evidence of radiculopathy, acute spinal cord compression (e.g., sudden bowel/bladder disturbance)
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Suspected systemic disorders (primary tumors, drop metastases, osteomyelitis)
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Postoperative evaluation of lumbar spine: disk vs. scar
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Localized back pain with no radiculopathy (leg pain)
Lumbar spine imaging requires a special spine coil. often used whole spine array coils have the advantage that patients do not need other positioning if also upper parts of the spine should be scanned. Sagittal T1 and T2 weighted FSE sequences are the standard views. With multi angle oblique techniques individually oriented transverse images of each intervertebral disc at different angles can be obtained.
See also the related poll result: ' MRI will have replaced 50% of x-ray exams by' | | | | | | | | | | | Further Reading: | | Basics:
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From Siemens Medical Systems;
Received FDA clearance in 2010.
MAGNETOM Skyra is a top-of-the-line, patient friendly wide bore 3 Tesla MRI system.
The system is equipped with the Tim 4G and Dot system (Total imaging matrix and Day optimizing throughput), to enhance both productivity and image quality with the complete range of advanced applications for clinical routine and research. Tim 4G features lighter, trimmer MRI coils that take up less space inside the magnet but deliver a high coil element density with increased signal to noise ratio and the possibility to use high iPAT factors.
Device Information and Specification
CLINICAL APPLICATION
Whole Body
Head, spine, torso/ body coil, neurovascular, cardiac, neck, shoulder, knee, wrist, foot//ankle and multi-purpose flex coils. Peripheral vascular, breast, shoulder.
CHANNELS (min. / max. configuration)
48, 64, 128
Chemical shift imaging, single voxel spectroscopy
MINIMUM TE
3D T1 spoiled GRE: 0.22 (256 matrix), Ultra-short TE
At isocenter: L-R 70 cm, A-P (with table) 55 cm
MAGNET WEIGHT (gantry included)
5768 kg
DIMENSION H*W*D (gantry included)
173 x 231 x 219 cm
COOLING SYSTEM
Water; single cryogen, 2 stage refrigeration
3 linear with 20 coils, 5 nonlinear 2nd-order
POWER REQUIREMENTS
380 / 400 / 420 / 440 / 460 / 480 V, 3-phase + ground; 110 kVA
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( MRA) Magnetic resonance angiography is a medical imaging technique to visualize blood filled structures, including arteries, veins and the heart chambers. This MRI technique creates soft tissue contrast between blood vessels and surrounding tissues primarily created by flow, rather than displaying the vessel lumen. There are bright blood and black blood MRA techniques, named according to the appearance of the blood vessels. With this different MRA techniques both, the blood flow and the condition of the blood vessel walls can be seen. Flow effects in MRI can produce a range of artifacts. MRA takes advantage of these artifacts to create predictable image contrast due to the nature of flow.
Technical parameters of the MRA sequence greatly affect the sensitivity of the images to flow with different velocities or directions, turbulent flow and vessel size.
This are the three main types of MRA:
All angiographic techniques differentially enhance vascular MR signal. The names of the bright blood techniques TOF and PCA reflect the physical properties of flowing blood that were exploited to make the vessels appear bright. Contrast enhanced magnetic resonance angiography creates the angiographic effect by using an intravenously administered MR contrast agent to selectively shorten the T1 of blood and thereby cause the vessels to appear bright on T1 weighted images.
MRA images optimally display areas of constant blood flow-velocity, but there are many situations where the flow within a voxel has non-uniform speed or direction. In a diseased vessel these patterns are even more complex. Similar loss of streamline flow occurs at all vessel junctions and stenoses, and in regions of mural thrombosis. It results in a loss of signal, due to the loss of phase coherence between spins in the voxel.
This signal loss, usually only noticeable distal to a stenosis, used to be an obvious characteristic of MRA images. It is minimized by using small voxels and the shortest possible TE. Signal loss from disorganized flow is most noticeable in TOF imaging but also affects the PCA images.
Indications to perform a magnetic resonance angiography ( MRA):
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Detection of aneurysms and dissections
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Evaluation of the vessel anatomy, including variants
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Blockage by a blood clot or stenosis of the blood vessel caused by plaques (the buildup of fat and calcium deposits)
Conventional angiography or computerized tomography angiography (CT angiography) may be needed after MRA if a problem (such as an aneurysm) is present or if surgery is being considered.
See also Magnetic Resonance Imaging MRI. | | | | | | | | | | | • View the DATABASE results for 'Magnetic Resonance Angiography MRA' (3).
| | | • View the NEWS results for 'Magnetic Resonance Angiography MRA' (10).
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The paramagnetic water-soluble metallofullerenes (Gd-fullerenols), which have strong T1 shortening effect, can be used as a novel core material of MRI contrast agents. Gadolinium endohedral metallofullerenes have been synthesized as polyhydroxyl forms (Gd@C82(OH)n, Gd-fullerenes) with the evaluation of their paramagnetic properties. The modification to the water-soluble forms is essential for the biomedical application of the metallofullerenes. The in vitro water proton relaxivity, R1 (the effect on 1/ T1), of Gd-fullerenes is significantly higher (20-folds) than that of commercial MRI contrast agents - e.g. Gd-DTPA. | | | | • View the NEWS results for 'Metallofullerenes' (1).
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