[Insight-users] Extract an oblique 2D slice from a 3D volume

[Luis Ibanez]

Hi Gheorghe


           Mmm, you didn't do your homework.


    You have not read the ITK Software Guide chapter.



Should you have read the chapter, you could have found that you
can compute a single slice as the output of the resampling by
just selecting an image grid of dimensions ( N x M x 1 ).

... and you could have avoided jumping to the *incorrect*
     conclusion that this is an inefficient method...



You *don't need to resample the entire volume*, you can define the
exact grid of points for which pixel values are to be computed.


Please read the ITK Software Guide


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

Section 6.9.4 "Resample Image Filter", pdf-pages 254-284.


What you need is to define a rigid 3D transform, and to setup
an Output image grid of dimensions N x M x 1.




Beware of the Aristotelian syndrome:


          "Too much idle thinking...
           not enough experimentation"




   Regards,


       Luis



----------------------------
Gheorghe Postelnicu wrote:
> Hi Luis,
> 
> Thanks for the suggestion. My prototype solution will indeed use the
> aproach you suggest. However, it is obviously inefficient, as it will
> resample the entire volume, when I will only need one slice.
> Additionally, it presents the disadvantage of increasing the number of
> necessary interpolations: to get the pixel value at a position, 2
> interpolations (instead of one) will be necessary.
> 
> That is why I was thinking that an image wrapper class would be great.
> If you can suggest an example or a skeleton of the methods that I
> would need to write to make this happen, I would be more than happy to
> contribute the code resulting.
> 
> Thanks,
> 
> On 5/7/07, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> 
>>
>>
>> Hi Gheorghe
>>
>>
>> You may want to use the
>>
>>              ResampleImageFilter
>>
>>
>> You will have to provide the Transform that defines the resampling
>> plane, and the parameters of the image grid that you want to use
>> for the 2D image.
>>
>> Please read the ITK Software Guide
>>
>>
>>       http://www.itk.org/ItkSoftwareGuide.pdf
>>
>>
>> in particular the section on "Geometric Transformations".
>>
>> This section describes how you can set the parameters of a
>> resampling problem.
>>
>>
>>
>>      Regards,
>>
>>
>>        Luis
>>
>>
>>
>> ---------------------------
>> Gheorghe Postelnicu wrote:
>> > Hi,
>> >
>> > I am looking into ways to extract an oblique 2D slice from a 3D
>> > volume. This is to be part of an iterative algorithm, so it would be
>> > great to be able to setup an image wrapper that would emulate a 2D
>> > image only sampling pixels when necessary. It would actually be great
>> > if I were able to call a registration filter on one of these image
>> > objects.
>> >
>> > The closest filter I found was ExtractImageFilter, but I don't think
>> > it fulfills the requirements I have tried to expose above.
>> >
>> > It would be great if someone could provide some guidance on the
>> > methods I would need to overwrite when writing a wrapper for a class
>> > that would emulate a 2D oblique slice of a 3D volume or any other
>> > method that would efficiently achieve this.
>> >
>> > Thanks,
>>
> 
>