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| Result: Searchterm 'MRI'
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Reader Mail
Wed. 12 Dec.07,
10:07
[Reply (1 of 2) to:
'double ir physic'
started by: 'soontorn siriserussa'
on Sun. 2 Dec.07]
 Category:
Sequences and Imaging Parameters
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| double ir physic |
Different types of double inversion recovery (DIR, 2IR) sequences are used to improve the suppression of blood signal (black blood technique) or to null the signals from two different tissue types (e.g. white matter and cerebrospinal fluid).
The black blood technique (used in cardiovascular MRI) works with two inversion pulses, where the first pulse is nonselective and the second pulse is slice-selective. TI is set to a value at which the signal of the recovering inverted blood is zero (http://www.mr-tip.com/serv1.php?type=db1&dbs=Double%20Inversion).
The second technique (also named gray matter only) is used in brain imaging to improve the detection of lesions, for example in the diagnostic of multiple sclerosis. Two 180° pulses with different TI are used to suppress two different types of tissue simultaneously.
Hope this helps
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|  View the whole thread | | |
Fritz y
Wed. 5 Dec.07,
13:04
[Start of:
'How to measure air volume in part of the trachea or the nose!'
0 Reply]
Category:
Sequences and Imaging Parameters
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| How to measure air volume in part of the trachea or the nose! |
Hi
I´m trying measure air volume in 3D and 2D space on a MRI scan.
What program is good to performe this measurement?
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Paul Tesla
Fri. 16 Nov.07,
08:55
[Reply (1 of 4) to:
'Haste and Rare sequences'
started by: 'Elena sussi'
on Tue. 13 Nov.07]
Category:
Sequences and Imaging Parameters
|
| Haste and Rare sequences |
RARE is the Generic name for TSE or FSE. So I guess you should say "Single-shot RARE with half fourier acquisition".
source: MRI. From picture to proton. D.W McRobbie
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| | View the whole thread | | |
Paul Tesla
Fri. 9 Nov.07,
15:31
[Start of:
'How do you measure SNR?'
0 Reply]
Category:
Basics and Physics
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| How do you measure SNR? |
I know this is a basic question but how do you measure SNR?
This page:
http://dnl.ucsf.edu/users/dweber/dweber_docs/mri_quality.html
tells me to measure an as small as possible ROI for the signal mean and as large as possible ROI for the standard deviation.
But I have a book called "MRI from picture to proton": This says that the standard deviation of the noise (Sn) can be measured using the mean or standard deviation (sd) of a background region. Then you can use the relationship:
Mean = 1.25 Sn
sd = 0.66 Sn
to find Sn. But where do the values 1.25 and 0.66 come from?
It also says that the measured mean of the signal ROI is related to the MR signal instensity (S) using:
Mean = sqrt(S^2 + Sn^2)
But why do they add up quadratically?
Thankyou for your help. Please leave a message or email me,
Paul
-------------
mri.tesla@gmail.com
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bob smith
Wed. 17 Oct.07,
06:41
[Reply (1 of 2) to:
'does the metaloceramic dental crowns are problem for MRI'
started by: 'Dimitar Todorov'
on Thu. 9 Mar.06]
Category:
Safety
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| does the metaloceramic dental crowns are problem for MRI |
hey everyone
I had an MRI (1.5 Tesla) and I have a dental crown and bridge, and metal fillings. I think I have the metal bonding porcelain crowns made with Nickel-Chromium, but it doesn’t matter. You will feel nothing. It doesn’t matter if you have titanium, or anything else. The MRI people are more worried about metal in soft tissue which can move around during the scan. Anything on your teeth or bone is fixed and therefore won’t cause problems. And for the patient, who cares about pain / discomfort, there is none, you’ll experience no sensation at all due to dental work.
Hope this helps
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