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Result : Searchterm 'brain imaging' found in 0 term [ ] and 2 definitions [ ], (+ 20 Boolean[ ] results
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Searchterm 'brain imaging'
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| Perfusion Imaging |   |
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(PWI - Perfusion Weighted Imaging) Perfusion MRI techniques (e.g. PRESTO - Principles of Echo Shifting using a Train of Observations) are sensitive to microscopic levels of blood flow. Contrast enhanced relative cerebral blood volume (rCBV) is the most used perfusion imaging.
Both, the ready availability and the T2* susceptibility effects of gadolinium, rather than the T1 shortening effects make gadolinium a suitable agent for use in perfusion imaging. Susceptibility here refers to the loss of MR signal, most marked on T2* (gradient echo)-weighted and T2 (spin echo)-weighted sequences, caused by the magnetic field-distorting effects of paramagnetic substances.
T2* perfusion uses dynamic sequences based on multi or single shot techniques. The T2* (T2) MRI signal drop within or across a brain region is caused by spin dephasing during the rapid passage of contrast agent through the capillary bed. The signal decrease is used to compute the relative perfusion to that region. The bolus through the tissue is only a few seconds, high temporal resolution imaging is required to obtain sequential images during the wash in and wash out of the contrast material and therefore, resolve the first pass of the tracer. Due to the high temporal resolution, processing and calculation of hemodynamic maps are available (including mean transit time (MTT), time to peak (TTP), time of arrival (T0), negative integral (N1) and index.
An important neuroradiological indication for MRI is the evaluation of incipient or acute stroke via perfusion and diffusion imaging. Diffusion imaging can demonstrate the central effect of a stroke on the brain, whereas perfusion imaging visualizes the larger 'second ring' delineating blood flow and blood volume. Qualitative and in some instances quantitative (e.g. quantitative imaging of perfusion using a single subtraction) maps of regional organ perfusion can thus be obtained.
Echo planar and potentially echo volume techniques together with appropriate computing power offer real time images of dynamic variations in water characteristics reflecting perfusion, diffusion, oxygenation (see also Oxygen Mapping) and flow.
Another type of perfusion MR imaging allows the evaluation of myocardial ischemia during pharmacologic stress. After e.g., adenosine infusion, multiple short axis views (see cardiac axes) of the heart are obtained during the administration of gadolinium contrast. Ischemic areas show up as areas of delayed and diminished enhancement. The MRI stress perfusion has been shown to be more accurate than nuclear SPECT exams. Myocardial late enhancement and stress perfusion imaging can also be performed during the same cardiac MRI examination. |
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| Signa 3.0T™ |  |
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(Signa VH/i 3.0T)
With GE Healthcare
leading-edge technology in ultra-high-field imaging. The 3 T VH/i provides a platform for advanced applications in radiology, cardiology, psychology and psychiatry. Real-time image processing lets you acquire multislice whole brain images and map brain functions for research or surgical planning. And the 3 T Signa VH/i is flexible enough to provide clinicians with high performance they require. It can provide not only outstanding features in brain scanning and neuro-system research, but also a wide range of use in scanning breasts, extremities, the spine and the cardiovascular systems.
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Device Information and Specification |
| CLINICAL APPLICATION |
Whole body
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| CONFIGURATION |
Cylindrical - high homogeneity |
| SURFACE COILS |
T/R quadrature head, T/R quadrature body, T/R phased array extremity (opt) |
| SPECTROSCOPY |
Single voxel & 2D CSI proton |
| SYNCHRONIZATION |
ECG/peripheral, respiratory gating |
| PULSE SEQUENCES |
SE, IR, 2D/3D GRE, FGRE, RF-spoiled GRE, FSE, Angiography: 2D/3D TOF, 2D/3D phase contrast vascular |
| IMAGING MODES |
Single, multislice, volume study, fast scan, multi slab, cine, localizer |
| SINGLE SLICE |
100 Images/sec with Reflex100 |
| MULTISLICE |
100 Images/sec with Reflex100 |
| FOV |
1 cm to 40 cm continuous |
| SLICE THICKNESS |
2D 0.5-100mm in 0.1mm incremental |
| DISPLAY MATRIX |
1280 x 1024 |
| MEASURING MATRIX |
128x512 steps 32 phase encode |
| PIXEL INTENSITY |
256 gray levels |
| SPATIAL RESOLUTION |
0.02mm |
| MAGNET TYPE |
Superconducting |
BORE DIAMETER
or W x H |
55cm |
| MAGNET WEIGHT |
15102 kg incl. cryogen's |
| H*W*D |
260cm x 238cm x 265cm |
| POWER REQUIREMENTS |
480 or 380/415, 3 phase ||
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| COOLING SYSTEM TYPE |
Closed-loop water-cooled grad. |
| CRYOGEN USE |
Less than 0.14 L/hr liquid He |
| FIELD STRENGTH |
3 T |
| STRENGTH |
40mT/m |
| 5-GAUSS FRINGE FIELD, radial/axial |
5.4 m x 3.2 m |
| SHIMMING |
Superconductive + hi order active |
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| Fast Imaging with Steady Precession | |
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| Circle of Willis | |
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A large network of interconnecting blood vessels at the base of the brain that when visualized resembles a circle, the arteries effectively act as anastomoses for each other. This means that if any one of the communicating arteries becomes blocked, blood can flow from another part of the circle to ensure that blood flow is not compromised.
The circle of Willis is formed by both the internal carotid arteries, entering the brain from each side and the basilar artery, entering posteriorly. The connection of the vertebral arteries forms the basilar artery. The basilar artery divides into the right and left posterior cerebral arteries.
The internal carotid arteries trifurcate into the anterior cerebral artery, middle cerebral artery, and posterior communicating artery.
The two anterior cerebral arteries are joined together anteriorly by the anterior communicating artery. The posterior commicating arteries join the posterior cerebral arteries, completing the circle of Willis.
The time of flight angiography MRI technique allows imaging of the circle of Willis without the need of a contrast medium (best results with high field MRI). A cerebrovasular contrast enhanced magnetic resonance angiography (MRA) depicts the circle of Willis in addition to the vessels of the neck (carotid and vertebral arteries) with one bolus injection of a contrast agent.
For Ultrasound Imaging (USI) see Cerebrovascular Ultrasonography at US-TIP.com.
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| Bird Cage Coil | |
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A RF coil, often a transmit receive coil with a number of wires running along the z-direction, arranged to give a cosine current variation around the circumference of the coil, which looks like a bird cage.
The bird cage coil works on a different principle to conventionally tuned local and surround coils in that it behaves like a tuned transmission line with one complete cycle of standing wave around the circumference. The frequency supply is generated by an oscillator, which is modulated to form a shaped pulse by a product detector controlled by the waveform generator. The signal must be amplified to 1000's of watts. This can be done using either solid state electronics, valves or a combination of both.
The bird cage coil design provides the best field homogeneity of all RF imaging coils.
One advantage is that it is simple to produce an exceedingly uniform B1 radio frequency field over most of the coil's volume, with the result of images with a high degree of uniformity.
A second advantage is that nodes with zero voltage occur 90° away from the driven part of the coil, thus facilitating the introduction of a second signal in quadrature, which produces a circularly polarized radio frequency field.
This type of volume coil is used for brain (head) MRI, or MR imaging of joints, such as the wrist or knees.
See also the related poll result: '3rd party coils are better than the original manufacturer coils' |
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