different scanning parameters

Submitted by Emilia Cheladze on Sun, 07/17/2016 - 20:27

Hi!

I am doing an analyses on two groups of subjects with data that was acquired with different scanning parameters:

1. TR 2.3, 37 slices, 3x3x3

2. TR 2.3, 34 slices, 4x4x4

What would be the best common voxel size for the analyses? 

To what point should I preprocess the data separately?

Thank you for any hepl in advance,

Emilia Cheladze

Forums:

YAN Chao-Gan

Wed, 07/20/2016 - 06:51

From the data, I would choose 4x4x4 for comparison. Although 3x3x3 is the most common resolution used.

Best,

Chao-Gan

Emilia Cheladze

Mon, 07/25/2016 - 10:06

Thank you very much for your answer!

If you don't mind I have few follow up questions, though.

1. What exactly happens in DPRSFA when I input the voxel size during Normalization step? Is the image actually resliced (if the input voxel size is different that it actually is) ? If yes, than could you please write what is the interpolation method?

2. If I were to reslice image in utilities>image reslicer when is the best moment to do it? Before/after preprocessing, first level?

3. What the choice of the interpolation method depends on? What would be the one you recommend? 

Emilia Cheladze

Mon, 07/25/2016 - 10:06

Thank you very much for your answer!

If you don't mind I have few follow up questions, though.

1. What exactly happens in DPRSFA when I input the voxel size during Normalization step? Is the image actually resliced (if the input voxel size is different that it actually is) ? If yes, than could you please write what is the interpolation method?

2. If I were to reslice image in utilities>image reslicer when is the best moment to do it? Before/after preprocessing, first level?

3. What the choice of the interpolation method depends on? What would be the one you recommend? 

YAN Chao-Gan

Wed, 07/27/2016 - 01:28

1. DPARSFA call's SPM's normalize function. You can find the details at SPM's manual. The interpolation is 4th Degree B-Spline (the default one).

2. You don't need to use Image Reslicer if you set the voxel size in Normalization.

3. I will choose the default one.

Emilia Cheladze

Fri, 08/12/2016 - 13:59

Thank you very much for your answer.
Let me ask once again, just to make sure I'm not going to make a mistake. 
Just by inputting the same voxel size (for example 4x4x4 for both data sets) I will reslice the images of one data set and not of the one that was already acquired 4x4x4. Therefore, I will end up having two sets of data acquired with different scanning parameters but in a form that can be analyzed together/compared. Is that correct? 

YAN Chao-Gan

Thu, 08/18/2016 - 00:52

Yes.

However, you have to resample the 4x4x4 data in the normalization step, though keep the same voxel size.