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| Result: Searchterm 'Noise'
found in 14 messages |
| Result Pages: 1 [2] 3 |
More Results:  Database (86) News Service (14) |
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Katelin Lyons
Fri. 3 Jun.11,
11:55
[Reply (1 of 2) to:
'Dixon technique'
started by: 'Reader Mail'
on Wed. 1 Jun.11]
 Category:
Sequences and Imaging Parameters
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| Dixon technique |
Dixon technique uses alternative water/fat phase-encoding strategies. The technique is generalized to phase encoding of theta radians, and the signal-to-noise ratio (S/N) performance is evaluated.To get some more information regarding this please check out the following link : http://www.ncbi.nlm.nih.gov/pubmed/18777528
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|  View the whole thread | | |
Robert Patten
Thu. 3 Mar.11,
22:08
[Start of:
'Building 3d Volumes from MRI DICOM'
4 Replies]
Category:
General
|
| Building 3d Volumes from MRI DICOM |
I have a number of MRI and CTs since a bad accident. I am a Mechanical Engineer with an electrical, power and computer background.
I was able to render the CT to 3D using Onis (not sure if you've seen this program), but have been unable to manage it with any of the MRIs.
The MRIs were taken on a Phillips Intera 1.5T
I can render a volume but only (1) of the (3) 2D images are clear before it is rendered and the resulting 3D image is just noise. I've tried various software packages and spent a lot of time with the software. Perhaps I don't have the required image files.
Maybe someone knows the answer.
Thanks,
Bob
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Sue Wong
Wed. 28 Jan.09,
20:03
[Reply (1 of 2) to:
'Gradient modes'
started by: 'Angela Hoskinson'
on Thu. 22 Jan.09]
Category:
Applications and Examinations
|
| Gradient modes |
You pay for the noise reduction; the parameter 'whisper' reduces the gradient performance. Db/dt (and the noise of the scanner is depended on db/dt) is directly proportional to the gradient performance (slew rate).
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| | View the whole thread | | |
Hugo Robalo
Thu. 3 Apr.08,
16:22
[Reply (2 of 4) to:
'MRI Bandwidth and turbo factor relation ?'
started by: 'young bong we'
on Thu. 20 Mar.08]
Category:
Basics and Physics
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| MRI Bandwidth and turbo factor relation ? |
A higher BW will increase the noise, minimum FoV, slices per TR and will decrease the minimum TE, SNR and echo spacing.
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Paul Tesla
Fri. 9 Nov.07,
15:31
[Start of:
'How do you measure SNR?'
0 Reply]
Category:
Basics and Physics
|
| 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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