Error in extracting

An error occur when I using ROI signal extracter:

You have to reslice your mask using Utilities->Image Reslicer.

Thank you very much!

Dear professor Yan,

My data are structural MRI data. 

and I also wanna extract Gray Matter or White Matter 116 ROI region signals applied by AAL mask.  
You said reslice mask using 
Utilities->Image Reslicer? instead of reslice the original structural MRI data ? and what's the difference between the 2 steps ?

Relicing mask is better as you will leave your data intact.

Dear Professor Yan,

Thank u for your reply!

soo, what i have to do is reslice the AAL templates according to the original data? 

just like if my original data size is 121X145X121. and I have to turn AAL templates(181X217X181) into 121X145X121.

Is there anything wrong ? 

Thank u again for your help.

Hello, Professor Yan.

sorry to bother u again. I wanna know : is there anything wrong with my thoughts ? and how could I get the sum of values(each brain region)

Reslice to the resolution of the data you want to extract.

Thank you very much, Professor Yan.

soo. what  I said is right? reslice the AAL template to the resolution of data.