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| Result: Searchterm 'Signa'
found in 79 messages |
| Result Pages: 1 2 3 4 5 [6] 7 8 9 10 11 12 13 14 15 16 |
More Results:  Database (382) News Service (60) Resources (16) |
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shruti soni
Wed. 27 Feb.13,
00:25
[Start of:
'STIR and l-spine'
1 Reply]
 Category:
Sequences and Imaging Parameters
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| STIR and l-spine |
we have got new spine coil for our 1.5 T philips achieva scanner. App came in and added new software and protocoal for that. when we run STIR sequence for l- spine with regular size patient, it comes out nice. However, with hypersthenic patient, it comes out very dark, suppressing signal from bone,fat and only shows csf in cord. could it be that TI not optimal for hypersthenic patient?
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adam wootton
Fri. 13 Apr.12,
17:35
[Reply (1 of 3) to:
'intracranial cavity volume'
started by: 'adam wootton'
on Fri. 13 Apr.12]
Category:
Applications and Examinations
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| intracranial cavity volume |
Correction. I am on a GE Signa HDx 3.0T with 15X software
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adam wootton
Fri. 13 Apr.12,
17:31
[Start of:
'intracranial cavity volume'
2 Replies]
Category:
Applications and Examinations
|
| intracranial cavity volume |
Hello,
As part of a clinical trial, I have been asked to calculate Intracanial cavity volumes as well as whole brain, total gray matter, and total white matter volume.
I am on a GE Signa 3.0T running 15x software.
Can anyone give me a clue on how to do this?
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Steven Ford
Tue. 31 Jan.12,
08:19
[Reply (1 of 2) to:
'RF shimming'
started by: 'Reader Mail'
on Thu. 1 Oct.09]
Category:
Basics and Physics
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| RF shimming |
For Magnetic fields, the overall field is adjusted to push it up a little bit in one spot and push it down a little bit in another area. The goal is to create a field that's perfectly homogenous.
The RF field created by the transmit coil likewise must be as homogenous as possible, so that the flip angle is constant throughout the imaging volume. In the past, designers have solved this problem by building coils such as the 'birdcage' style that would create a very even amount of energy inside. This is one reason why the transmit coils tend to be large.
With the advent of 3 Tesla and stronger magnets, the RF resonant frequency also rises. RF energy absorbed in the patient rises with the higher frequencies also, and another problem raises its head: it's a lot harder to make a very homogenous RF field. Even if you are scanning phantoms, the inside tends to be subject to different energy than the edges.
But in the human body, there are all sorts of irregular lumps and bumps that absorb RF differently, further complicating matters.
Now, on modern scanners it's possible to perform a magnetic field shim with the patient actually in the magnet in order to compensate for minute changes in the magnet from one exam to another. For super-high field magnets, an RF shim is also a handy thing to do.
If you have a Multi element RF transmit coil (regular phased array coils are just for receiving) you can run a program which selectively turns up the power in some elements so that the overall signal received is maximized. That's an RF shim.
Steven Ford
Professional Imaging Services, Inc.
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Anna Lena Golay
Wed. 25 Jan.12,
20:59
[Reply (3 of 7) to:
'Imaging optic neuritis'
started by: 'Karen Lesley'
on Wed. 18 Jan.12]
Category:
General
|
| Imaging optic neuritis |
A 2-3 mm STIR sequence through the optic nerves may show the characteristic high-signal intensity of optic neuritis. Gadolinium enhanced T1-weighted fat-saturated (to suppress the bright signal of the orbital fat tissue) images of the orbits show the inflammation of the optic nerve. White matter lesions, which denote a higher risk of developing MS, are typical imaged with FLAIR and T2-weighted images (hyperintense lesions), or show enhancement of T1-weighted images postcontrast.
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