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From GE Healthcare;
The Signa SP 0.5T™ is an open MRI magnet that is designed for use in interventional radiology and intra-operative imaging. The vertical gap configuration increases patient positioning options, improves patient observation, and allows continuous access to the patient during imaging.
The magnet enclosure also incorporates an intercom, patient observation video camera, laser patient alignment lights, and task lighting in the imaging volume.
Device Information and Specification CLINICAL APPLICATION Whole body Integrated transmit and receive body coil; optional rotational body coil, head; other coils optional; open architecture makes system compatible with a wide selection of coilsarray Standard: SE, IR, 2D/3D GRE and SPGR, 2D/3D TOF, 2D/3D FSE, 2D/3D FGRE and FSPGR, SSFP, FLAIR, EPI, optional: 2D/3D Fiesta, true chem sat, fat/water separation, single shot diffusion EPI IMAGING MODES Localizer, single slice, multislice, volume, fast, POMP, multi slab, cine, slice and frequency zip, extended dynamic range, tailored RF TR 1.3 to 12000 msec in increments of 1 msec TE 0.4 to 2000 msec in increments of 1 msec 2D: 1.4mm - 20mm 3D: 0.2mm - 20mm POWER REQUIREMENTS 200 - 480, 3-phase | | | | | Further Reading: | News & More:
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Time-dependent electromagnetic fields are significantly attenuated by conducting media (including the human body); the skin depth gives a measure of the average depth of penetration of the RF field.
A high power frequency tunable RF source can be rapidly switched on and off. This produces a large RF field perpendicular to the magnetic field. This RF field is focused by the body coil. The RF source and coils must be tunable in both frequency and impedance to
'match the impedance' of the patient's body.
The skin depth may be a limiting factor in MR imaging at very high frequencies (high magnetic fields). The skin depth also affects the Q of the coils.
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Every tissue in the human body has its own T1 and T2 value. This term is used to indicate an image where most of the contrast between tissues is due to differences in the T1 value.
This term may be misleading in that the potentially important effects of tissue density differences and the range of tissue T1 values are ignored.
If the machine parameters are chosen, so that TR less than T1 (typically under 500 ms) and TE less than T2 (typically under 30 ms), a power series expansion of the exponential functions and then neglecting second and higher order terms yields
Mxy = Mxy0 TR/T1
thus the expression becomes independent of T2 and yields the condition for T1 weighting.
Therefore a T1 contrast is approached by imaging with a short TR, compared to the longest tissue T1 of interest and short TE, compared to tissue T2 (to reduce T2 contributions to image contrast). Due to the wide range of T1 and T2 and tissue density values that can be found in the body, an image that is T1 weighted for some tissues may not be so for others.
Lesions with short T1 are (bright in T1 weighted sequences):
fat (lipoma, dermoid)
sub-acute haemorrhage (metHb)
paramagnetic agent (Gd, pituitary)
protein-containing fluid (colloid cyst)
metastatic melanoma (melanotic). | | | | | | • View the DATABASE results for 'T1 Weighted' (56).
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(T/R) Also called transceiver coil. An RF coil that acts as a transmitter (T) producing the B1 excitation field and as a receiver (R) of the MRI signal. Such a coil requires a T/R switching circuit to switch between the two modes. A body coil is typically a T/R coil, but smaller volume T/R coils (head/extremities) are often used at high field as a possibility of reducing RF power absorption (SAR). | | | | | | • View the DATABASE results for 'Transmit Receive Coil' (4).
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From FONAR Corporation;
in October of 2004, the company changed the product name of the Stand-Up™ MRI to the Upright™ MRI. The Indomitable™, Upright™ MRI is the only open MRI in the world that can perform positional MRI (pMRI), i.e. the Upright MRI™ scans patients in upright, weight-bearing positions, in addition to the conventional lie-down positions. The Upright™ MRI is the only device that can scan patients in the position their symptoms occur, in their position of pain. In early clinical reports independently confirm the effectiveness and potential of positional MRI. In October 2000, Fonar received permission to market the Indomitable™ from the FDA.
Device Information and Specification CLINICAL APPLICATION Whole body -
weight-bearing MRI -
position imaging (flexion, extension, bending, standing, sitting and recumbent scanning)
CONFIGURATION Front-open and Top-open MRIPOWER REQUIREMENTS 380/400/415/440/480 V COOLING SYSTEM TYPE Water, closed-loop | | | | • View the DATABASE results for 'Upright™ MRI' (5).
| | | • View the NEWS results for 'Upright™ MRI' (9).
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