[Insight-users] Control of deformation field generation via landmarks?

[Luis Ibanez]

Hi Ruben,

Thanks for the update.

Your explanation makes sense.




On the bad news:

There are no filters for performing this extrapolation
from a set of landmarks.


It will be great if you can write one and contribute it
to the Insight Journal:

         http://www.insight-journal.org/


You may want to read:
http://www.itk.org/Wiki/ITK_Procedure_for_Contributing_New_Classes_and_Algorithms#The_Procedure



    Thanks



       Luis


=======================
Ruben Schilling wrote:
> Hi Luis,
> 
> I tested actually all 5 Kernel transforms in ITK for this and I  
> discovered my problem actually is, that there are no landmarks on the  
> border of the image. Thus the splines fold however they like to fold  
> outside of the small landmarks regions. The interpolation near my  
> landmark positions looks very good though.
> I guess what I need is a more or less isotropic copy process (maybe  
> with slight averaging) of the few displacement vectors I have to  cover 
> all of the image foreground. Is there a filter to do an  isotropic 
> masked extrapolation of a sparse deformation field? If not  I probably 
> need to write one myself.
> 
> Regards,
> Ruben
> 
> 
> 
> Am 11.07.2007 um 18:44 schrieb Luis Ibanez:
> 
>> Hi Ruben,
>>
>> The KernelTransform used inside this filter *already* blends
>> the deformation from one landmark to the next.
>>
>> You may want to play with replacing the reciprocal elastic body
>> kernel with the elastic body one.
>>
>> If you want to see profiles of the different kernels you can
>> use the application:
>>
>>         InsightApplications/ThinPlateSplines
>>
>>
>> You should also play with the value of Stiffness. This parameter
>> allows to modify the behavior of the KernelTransform from
>> interpolation to approximation. The default behavior is to
>> interpolate.
>>
>>
>> When applying deformations it is wise to add landmarks on the
>> outside of the image, and to have their homologous landmarks
>> to be superimposed, so that they generates a constrain of
>> zero deformation around the image.
>>
>>
>>
>> Regards,
>>
>>
>>     Luis
> 
> 
>