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| Result: Searchterm 'Bit'
found in 15 messages |
| Result Pages: 1 [2] 3 |
More Results:  Database (35) News Service (35) Resources (8) |
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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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|  View the whole thread | | |
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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| | View the whole thread | | |
Jack McIntire
Tue. 25 Oct.11,
18:53
[Reply (5 of 7) to:
'MRI Magnet Room Cameras?'
started by: 'David Pierce'
on Thu. 22 Sep.11]
Category:
Equipment
|
| MRI Magnet Room Cameras? |
The system is simple to use, but d@mn helpful. It comes with instructions, and even then I can be a bit thick, so I've called for help with the stereo bit. They didn't mind helping me out over the phone, and when we found the problem I realized how little I use technology outside of my field.rnrn The install took about an hour and a half, but the engineer for our building said it was easy - and that didn't cut too bad into scan time. We just made sure it was a slow day when we decided to install. rnrn We went through this company: SoundImaging.com We had used them for upgrades and parts before, so we knew who we were talking to and that we could trust the equipment.
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| | View the whole thread | | |
Katelin Lyons
Fri. 27 May.11,
09:51
[Reply (1 of 2) to:
'Career as a Physician'
started by: 'Aaliah Thomas'
on Fri. 27 May.11]
Category:
General
|
| Career as a Physician |
Yes its true a physician's career is on high demand. With the growth in population and growth in medical sectors job opportunities are rising.To be a successful physician one should keep the following things in mind:
*Doctors must have a very strong grasp of math and science, chemistry and biology, and be able to analyze information and solve problems.
*Should exhibit excellent interpersonal skills in order to communicate effectively with patients and their families.
*Must be able to think quickly on their feet, and make critical decisions accurately and efficiently.
*If he aims to go into private practice and own a health care business, it would be helpful to have a basic understanding of business and accounting principles as well.
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| | View the whole thread | | |
Karen Lesley
Sat. 21 May.11,
16:03
[Start of:
'Best pulse sequences for spinal cord demyelination?'
3 Replies]
Category:
Applications and Examinations
|
| Best pulse sequences for spinal cord demyelination? |
Hi all. I wonder if you can help? A friend has asked me to recommend the best protocols to detect demyelination. She is about to pay a fortune for a private 3T scan and doesn't want to waste her money. Problem is, although I know a fair bit about the brain, I know next to nothing about the spinal cord! I understand that FLAIR is not optimal in the spinal cord, but I'm getting mixed messages about what is from my reading. Is it FSE?! Any advice really gratefully received! Thanks :-)
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