|
Magnetic
Resonance -
Technology
Information
Portal |
Welcome to MRI Technology • |
|
|
 | Info
Sheets |
| | | | | | | | | | | | | | | | | | | | | | | | |
 | Out-
side |
| | | | |
|
| | | | | |
| Result: Searchterm 'Signa'
found in 78 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) |
|
|
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
|
| intracranial cavity volume |
Correction. I am on a GE Signa HDx 3.0T with 15X software
|
|  View the whole thread | | |
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?
|
| | View the whole thread | Reply to this thread
(login or register first) | |
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
|
| 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.
|
| | 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.
|
| | View the whole thread | | |
Adana Osco Barras
Tue. 3 Jan.12,
21:09
[Reply (1 of 2) to:
'Hyperintense blood vessels in SE'
started by: 'Peruvumba Jayakumar'
on Thu. 29 Dec.11]
Category:
Sequences and Imaging Parameters
|
| Hyperintense blood vessels in SE |
Prolonged T1 relaxation times, decreased T1 tissue contrast, and increased susceptibility rnare typical effects at high field MRI.rnDue to the longer T1 times at 3T, the signal rnintensity inside the vessels is preserved even in smaller vessels. Try TR 700, TE 10.rnInversion recovery sequences are very well suited for optimal gray to white matter contrast, but enhancement after administration of gadolinium may not be visible.
|
| | View the whole thread | |
| |
| | Result Pages : 1 2 3 4 5 [6] 7 8 9 10 11 12 13 14 15 16 | |
|
| |
 | Look
Ups |
| |
|
MR-TIP.com uses cookies! By browsing MR-TIP.com, you agree to our use of cookies. | | | [last update: 2024-02-26 03:41:00] |
|
|
bottom
top
