[Mristudio-users] Gradient table

Fri Apr 17 02:33:19 EDT 2009

Hi Eric,

For Philips scanner there are several types of gradient tables you can
specify in the scanner. Please check your protocol for the following points;

1)       Gradient table: High (32-orientation)/ Medium (15-orientation) /
Low (6-orientation)

2)       Overplus (ON / OFF)

3)       Oblique plane (X/Y/Z angles)

The first option has 3 choices and the second option has 2 choices.
Therefore, there are 3 x 2 = 6 gradient tables.

If the second option (Overplus) is NO, the third option has no effect. If
the second option is YES, the gradient table has to be rotated based on the
oblique angles.

To simplify the DTI processing, we recommend Overplus = NO.

We have the basic 6 tables, which can be used as is if you use Overplus =
OFF or Oblique angles = 0/0/0 degree.

Please let us know which options you are using.

Susumu

  _____  

From: mristudio-users-bounces at mristudio.org
[mailto:mristudio-users-bounces at mristudio.org] On Behalf Of eric Q
Sent: Thursday, April 16, 2009 9:44 PM
To: mristudio-users at mristudio.org
Subject: Re: [Mristudio-users] Gradient table

Hello Dear DTIstudio users:

I am new to DTIstudio, I was hoping someone could give me some much needed
advises for beginners.

I was trying to obtain the FA values for my brain phantom (PHILIP 3T
scanner). When I clicked on "DTI mapping", it prompted me to enter the
"gradient table", how do I calculate the "gradient table"?

Thanks in advanced

Best regards

Eric

  _____  

Date: Thu, 9 Apr 2009 11:04:09 -0400
From: susumu at mri.jhu.edu
To: mristudio-users at mristudio.org
Subject: Re: [Mristudio-users] MriView3D application close

Hi Hugh,

When you got this error, please suspect one of the following two reasons;

1) Memory shortage:

Even if you have many GB of memories, 32-bit Windows system can allocate
only 1 - 1.5 GB to each program. To check if you have the memory problem,
please restrict the slices to be calculated. In the initial data parameter
window, there is a section called "Slices to be processed". Here you can
specify only a portion of slices to be processed. Please limit the slices
to, for example, 0-9 and see how it goes. If you can calculate tensors
without errors, then you have the memory problem. The solution is; a)
upgrade to the 64-bit system or b) devide the calculation to 2 batches (e.g.
slice 0-29 for the first batch and 30-59 for the second batch), calculate
all maps (e.g. FA), and later combine them.

2) Mismatch between the gradient table and the number of images:

For example, if you specify 12-orientation table and 30 volume images, then
you get the error. After loading the data and before you go to the Dti Map
tab, make sure that you have 1 b0 + 64 DWIs in the pull-down menu in the
right column of the Image tab. If you have the correct number of the images,
then you might have an error in your gradient table. Small mistakes such as
missing "," are often difficult to detect. The best way is; a) load the data
using DtiMapping under the "File" button on the top left, b) close the
window, c) open the image paremater window again by clicking "DtiMapping" in
the "File" button again, d) the window still remembers the gradient table
you entered last time. This remembered window tells how DtiStudio
interpreted your gradient table. If there is any syntax errors, you may find
them much easier. For example, if you enter, "4: 1 0.5 0", instead of "4: 1,
0.5, 0", then you would find, "4: 1, 0, 0".

If any of these do not solve the issue, please let us know.

Susumu

  _____  

From: mristudio-users-bounces at mristudio.org
[mailto:mristudio-users-bounces at mristudio.org] On Behalf Of Hugh Wang
Sent: Wednesday, April 08, 2009 6:30 PM
To: mristudio-users at mristudio.org
Subject: [Mristudio-users] MriView3D application close

Hi, 

I was using the dtistudio (ver. 2.4)  to look at the Siemens DICOM diffusion
images (1baseline,64 gradients). After successfully loading the images, I
click the "dti map" option at lower right corner. Whatever calculation I
choose, it always gives me an error: 

"MriView3D MFC Application has encountered a problem and needs to close.  We
are sorry for the inconvenience."

I tried several PCs, and the problem keeped the same. I would appreciate
that if there's anyone having any idea on how to solve it. Thanks.

Best,
Hugh

  _____  

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