how to extract ALFF-values?

Submitted by Marius on Tue, 03/04/2014 - 00:34

Dear all,

i am working with the REST toolbox V1.8 and i would like to know how i can extract ALFF-values out of a cluster which occured in a statistical result map. I need the ALLF-values from all the voxels inside this cluster of all my subjects.
 
Thanks for your help,

Marius

Submitted by Marius on Mon, 07/14/2014 - 17:55

Hey,

thank you for your advice!

I have extracted the alff-values for each voxel out of a roi for each of my subjects and i got values like this "-9670000000000000, -736000000000000, -5890000000000000 etc."
Are these values right and how can i interpret these?

Further i would like to correlate the alff-values with neuropsychological parameters, how would you do it?

With best regards,

Marius

Submitted by ZHANG_RESTadmin on Wed, 07/16/2014 - 11:33

 i would say these values are not correct ones.

 please make sure that you use the correct alff result images to extract roi signals, for example, you should use malff-1 or zalff as the input images for signal extraction. coz those results are correctly normalized or standardized which are proper for furhter statistical anaylses. 

 note that alff is a meansurement taht averaging the amplidue of fluctuation, the value should be positive, so the malff-1 should always be positive values, but zalff can be negative becasue the standardization way is different from that for malff-1.   I recommend you use malff-1.


Submitted by Marius on Thu, 07/17/2014 - 16:29

Hey,

i had used the zalff images as input images for the roi-signal extraction. I got positive and negative values but they dont looks normalized (-3601662756055500, 336363448244650 etc.). I have done the signal extraction with the malff-1 images and i got the same uncommon numbers (-1471842772160950, -6763529507998010) and they are all negative.

If you like i give you a sample of my datas and you could have a look at it.

Thanks,

Marius

Submitted by ZHANG_RESTadmin on Thu, 07/17/2014 - 23:14

 I would like to see the images you have now. 

 1. a sample of the raw nifiti formated fMRI data 
 2. a screenshoot of your dparsfa/rest processing setting up
 3. a sample of the preprocessed data
 4. your alff/zalff/malff/malff-1 images for a single subject

 My contact information is: napoleon1982@gmail.com 
 Thank you.

Submitted by ZHANG_RESTadmin on Wed, 07/16/2014 - 11:35

  i would say these values are not correct ones.



 please make sure that you use the correct alff result images to extract roi signals, for example, you should use malff-1 or zalff as the input images for signal extraction. coz those results are correctly normalized or standardized which are proper for furhter statistical anaylses. 



 note that alff is a meansurement taht averaging the amplidue of fluctuation, the value should be positive, so the malff-1 should always be positive values, but zalff can be negative becasue the standardization way is different from that for malff-1.   I recommend you use malff-1.

  if you want correlation analysis you can use SPSS to do it. becasue all the alff values you have extracted should be stored in a txt file.

Submitted by Marius on Thu, 07/17/2014 - 16:18

Hey,

i had used the zalff images as input images for the roi-signal extraction. I got positive and negative values but they dont looks normalized (-3601662756055500, 336363448244650 etc.). I have done the signal extraction with the malff-1 images and i got the same uncommon numbers (-1471842772160950, -6763529507998010) and they are all negative.

If you like i give you a sample of my datas and you could have a look at it.

Thanks,

Mariisu