[Insight-users] Re: MutualInformationImageToImageMetric: Lack of Transform Initialization

[Luis Ibanez]

Hi Malempati,

When you report the "size" of an image, you
should indicated in terms of the number of
pixels along every dimension.

For example:  1024 x 768 pixels.


The report:

            Size: 42496

is not very useful.


---

If you are *not initializing* the Transform,
then that's the source of your registration
problem.


At a minimum, you should initialize the Transform
in such a way that the centers of both images will
overlap.

For a description on how to do this
please read the ITK Software Guide

    http://www.itk.org/ItkSoftwareGuide.pdf

in particular the "Image Registration" chapter.

For instruction on how to initialize transforms
see, Section 8.6.1., pdf-pages 382-382,

As you will see, the computation involves the number
of pixels of the image along every dimension, the
pixel spacing and the origin.



    Regards,


        Luis



---------------------------------------
deepa_malempati at rediff.com wrote:
> Hi,
> Luis.
> The details of images are given below:
> 1:Fixedimage                           2:MovingImage
>   a.Size: 42496                            Size: 39277
>   b.Spacing: [1.2, 1.01562]         Spacing: [1, 1]
>   c.  Origin: [0, 0]                          Origin: [0, 0]
> And i'm using the Translation Transform.It is not Initialized with any values in the code.
> 
> Luis Ibanez wrote:
> 
>>
>>Hi Malempati,
>>
>>It is very unlikely that the source of the problem
>>is the size in Kilobytes of your images.
>>
>>
>>If you have an observer and the error message
>>appears before the observer reports on the first
>>iteration, then you can remove the Optimizer
>>as a suspect, and instead focus on the most
>>likely reasons;
>>
>>
>>   1) A poor initialization of the Transform.
>>
>>or
>>
>>   2) Invalid values of origin & spacing in the
>>      fixed and moving images.
>>
>>
>>Questions:
>>
>>1) What is the size of your images in pixels ?
>>2) What is the pixel spacing of each image ?
>>3) What is the origin of the images ?
>>
>>
>>You can get all this information by calling
>>
>>    reader->GetOutput()->Print( std::cout )
>>
>>
>>
>>Also:
>>
>>
>>4) What transform are you using ?
>>5) How are you initializing the Transform ?
>>
>>
>>
>>   Regards,
>>
>>
>>
>>      Luis
>>
>>
>>
>>-------------------------------------------
>>deepa_malempati at rediff.com wrote:
>>
>>>Hi,
>>>Luis,thanks for u'r reply.
>>>i have used the observer,but not even single iteration is getting
>>>performed.Would it be due to the size variation of the images.The sizes
>>>of the fixed image is 21KB and that of moving image is 6 KB.
>>>waiting for u'r reply,
>>>Thanking u,
>>>MALEMPATI.
>>>Luis Ibanez wrote:
>>>
>>>
>>>>
>>>>Hi Malempati:
>>>>
>>>>
>>>>1) Read the ITK Software Guide
>>>>
>>>>     http://www.itk.org/ItkSoftwareGuide.pdf
>>>>
>>>>   in particular the Image Registration chapter.
>>>>
>>>>
>>>>2) Make sure that your images have valid values
>>>>   of image origin and image spacing
>>>>
>>>>3) Make sure that you initialize the Transform
>>>>   parameters
>>>>
>>>>4) Add an observer to the Optimizer, and print
>>>>   out the values of the metric and transform
>>>>   parameters at every iteration.
>>>>
>>>>5) Identify how many iterations you manage to
>>>>   run before you get the error message.
>>>>
>>>>
>>>>
>>>>The error means that the Fixed and Moving images
>>>>have such small overlap that the registration
>>>>process can't continue.
>>>>
>>>>The problem may be caused by:
>>>>
>>>>a) incorrect image information
>>>>b) bad initialization
>>>>c) poor choices in the optimizer parameters
>>>>
>>>>
>>>>
>>>>  Regards
>>>>
>>>>
>>>>     Luis
>>>>
>>>>
>>>>
>>>>-------------------
>>>>MALEMPATI wrote:
>>>>
>>>>
>>>>>Hi, 
>>>>>all.how to get rid of this error given below. 
>>>>>
>>>>>itk::ERROR: MutualInformationImageToImageMetric(012C9D90): All the 
>>>>>sampled point mapped to outside of the moving image
>>>>
>>>>_______________________________________________
>>>>Insight-users mailing list
>>>>Insight-users at itk.org
>>>>http://www.itk.org/mailman/listinfo/insight-users
>>>>
>>>>
>>>
>>>Quoted from: 
>>>http://www.nabble.com/MutualInformationImageToImageMetric-tf3762435.html#a10652461
>>>
>>>
>>
>>_______________________________________________
>>Insight-users mailing list
>>Insight-users at itk.org
>>http://www.itk.org/mailman/listinfo/insight-users
>>
>>
> 
> Quoted from: 
> http://www.nabble.com/MutualInformationImageToImageMetric-tf3762435.html#a10664017
> 
>