[Camino-users] Spatially varying sigma

[Philip A Cook]

Hi,

Yes, you would scale all the data. I don't think it would change ADC in any way. 

A quick way to test this would be to divide all the data by your estimated global sigma, then run restore again with sigma == 1. You should see the same results as with the unscaled data and whatever sigma you used.



On Apr 23, 2015, at 3:33 PM, djpeters at u.washington.edu wrote:

> Hmm, that's interesting - you would have to scale the B0 also, right? Would there be any implications for the derived ADC values? What about doing tractography from such a scaled data set?
> 
> On Wed, 22 Apr 2015, Slater David wrote:
> 
>> Hi,
>> 
>> If you want to account for this I think you could just scale your raw DWI data if you have a noise map in the same space.
>> 
>> Perform the DWI distortion correction then divide the DWIs by the non-uniform noise std-map. In this way signal is scaled to match noise across the image and you can just give a noise std of 1 to camino (assuming your noise map was the std in each voxel).
>> 
>> Might need a little testing but it should work.
>> 
>> Best,
>> David
>> 
>> 
>> -----Message d'origine-----
>> De : camino-users-bounces at www.nitrc.org [mailto:camino-users-bounces at www.nitrc.org] De la part de djpeters at u.washington.edu
>> Envoyé : 21 April 2015 19:24
>> À : camino-users at public.nitrc.org
>> Objet : [Camino-users] Spatially varying sigma
>> 
>> Hello camino users,
>> 
>>   Is there any way to give RESTORE an image of sigma values, to take into account the spatially varying noise level due to parallel acquisition (i.e.
>> more noisy in the middle, less on the sides).
>> 
>> Thanks,
>> -Dan Peterson
>> 
>> 
>> 
>> 
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