[Insight-users] Help With Affine Transform

[Luis Ibanez]

Hi Huss,

If the final transform of your registration does not
contains a scaling effect that you were expecting it
means that you should readjust the parameter scaling
coefficients that regulate how much translation and
how much rotation/shearing/scaling your Affine transform
will tend to do when searching for better values of the
metric.

   optimizer->SetScales( optimizerScales );


Before you go and change those coefficients. Note that
the process of optimizing geometric scaling is even more
unstable than the process of optimizing rotation.

Therefore you probably want to let the Scaling refinement
for the final part of your registration.

Question 1:

     Is your registration, so far, solving correctly
     for translations and rotations ? and only missing
     to correct some scale ?


Question 2:

     How big is the scaling factor that you are expecting ?
     It is unlikely that a registration process will solve
     scaling factors smaller than 0.8 or larger than 1.2


Question 3:

     Did you made sure that your images have correct values
     in their Image Origin and Image Spacing ? This is absolutely
     critical for the registration process.

     Please post to the list the details of your images (both fixed
     and moving  images). Let us know how many pixels they have,
     where is their origin and what are their pixel spacings along
     each dimension.



Thanks


    Luis



-------------------------------
Huss wrote:

> Hi Luis 
> the program compiles and give me the output ..
> the problem is that I expect scaling which doesnt take place....
> I have incorporated the Affine Transform and GradientDescentOptimizer
> and I have made the necessary changes to the MultiResMIRegistration
> code.
> Please help me with this.
> 
> Thank You
> Huss
> 
> 
> On Mon, 02 Aug 2004 23:23:59 -0400, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> 
>>Hi Huss,
>>
>>Could you please be more precise and indicate what
>>kind of problem are you having with your code ?
>>
>>A) Is it compiling ?
>>   If not, please post the compilation errors.
>>
>>B) Is it crashing at run-time ?
>>   If so, please describe in what stage of the
>>   registration it crashes.
>>
>>C) Is it producing wrong registrations ?
>>   If so, please describe the effect that you
>>   observe on those registrations versus what you
>>   were expecting.
>>
>>Thanks
>>
>>     Luis
>>
>>-----------------
>>
>>
>>Huss wrote:
>>
>>
>>>Hello Everyone,
>>>
>>>I am using the MultiResMIRegistration package and I am trying to
>>>implement the Affine Transform and gradient descent optimizer. For
>>>some reason I am not able to implement the scaling for which I intend
>>>to use the Affine Transform for. I would really appreciate if someone
>>>can check and let me know whats wrong and if I made the correct
>>>changes. I am sending you the MIMRegistration.txt and
>>>MIMRegistration.h files and I have indicated the changes i made to
>>>implement Affine.
>>>
>>
>>
> 
>