[Insight-users] NormalizedCorrelationImageToImageMetric speedup

[Marius Staring]

Hi Andinet,

I was afraid I had to do that :) But see

    
http://www.insightsoftwareconsortium.org/InsightJournal/view_reviews.php?back=index.php&pubid=87

for the description and the source code.

Marius


Andinet Enquobahrie wrote:
> Hi Marius,
>
> Can you please write a short description of your improvements to the 
> NormalizedCorrelationImageToImageMetric class and submit your 
> description with the code to the InsightJournal.
>
> http://insightsoftwareconsortium.org/InsightJournal/
>
> thank you
>
> -Andinet
>
>> Hi all,
>>
>> The current GetDerivative() and GetValueAndDerivative() from the 
>> NormalizedCorrelationImageToImageMetric loop twice over the fixed 
>> image. This is not neccesary, one time is enough to calculate the 
>> metric value and the derivative to the transform parameters. I have 
>> rewritten this class to do so, and this gives the expected (almost) 
>> two times speedup.
>>
>> Also I have added the possibility to compute the metric over only a 
>> random subset of the fixed image pixels. This reduces the computation 
>> time (substantially), while convergence properties are maintained. It 
>> is similar to the MattesMutualInformationMetric, but there a fixed 
>> subset is used.
>>
>> I have added this code as an attachment. Feel free to commit it to 
>> the repository (the code also contains some small bug fixes). I have 
>> tested that, when using all pixels in the fixed image, the new code 
>> gives exactly the same output as the current itk code.
>>
>> I have also implemented the possibillity to use a random subset in 
>> the MeanSquaresImageToImageMetric (shouldn't that be called the 
>> MeanSquareDifferenceImageToImageMetric?) This is also attached.
>>
>> Regards,
>>
>> ------------------------------------------------------------------------
>>
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>>  
>>
>
>
>

-- 
Marius Staring
Image Sciences Institute
University Medical Centre Utrecht
Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
phone: +31 (0)30 250 3186, fax: +31 (0)30 251 3399
marius at isi.uu.nl, http://www.isi.uu.nl/People/Marius