[Insight-users] itkGradientDifferenceImageToImageMetric

[Bill Lorensen]

Vincent,
I have not really studied the metric in detail. There could still be bugs. 
I'll take a look over the next week or so. If you find out anything more, 
keep me posted,

Bill

At 12:16 PM 12/2/2005, Vicente Grau wrote:
>Thanks very much for the fix. It seems to work for me too.
>When I apply the metric to my images, it now produces values that vary 
>when I apply different translations. The variation, though, is so small 
>that I can't use to guide an optimizer. I have been looking at the code, 
>and I don't understant well how the calculation is done. It calculates the 
>metric as:
>
>A/(A + diff^2)
>
>where
>
>diff = grad1 - s*grad2
>
>Actually, this is done for each of the dimensions, and added up to obtain 
>the final result. Up to this point, it looks fine to me, and it 
>corresponds to the gradient difference as used, e.g., in [Penney et al, A 
>comparison of similarity measures for use in 2D-3D medical imaging 
>registration, IEEE TMI 17(4), 586-595.]
>Now the program tries several values of s, starting from zero, and stops 
>whenever it finds a maximum, i.e., when increasing the value of s produces 
>a decrease in the final result. For the images I have tried, this usually 
>occurs just at the first value of s (s=0), so the final result is the same 
>in most cases. I am probably missing something about how the algorithm 
>works. Are there any conditions for the input images (e.g., intensity 
>ranges)? Why is this search for the maximum performed?
>
>Again, thanks very much for your help.
>
>Vicente
>
>
>Lorensen, William E (Research) wrote:
>
>>Thanks for the bug report. I think I fixed it. It never worked apparently.
>>
>>You will need to update:
>>
>>Code/Commono/itkTranslateTransform.txx
>>Code/Algorithms/itkGradientDifferenceImageToImageMetric.txx and .h
>>Testing/Code/Algorithm/itkGradientDifferenceImageToImageMetricTest.cxx
>>
>>Now, the values change. I'm not sure if thet are correct. If you find 
>>that it works as expected (or not), let us know.
>>
>>Bill
>>
>>-----Original Message-----
>>From: Vicente Grau [mailto:vicente at robots.ox.ac.uk]
>>Sent: Thursday, December 01, 2005 11:42 AM
>>To: Lorensen, William E (Research); insight-users at itk.org
>>Subject: Re: [Insight-users] itkGradientDifferenceImageToImageMetric
>>
>>
>>Thanks very much, I have already placed a bug report (number 2543). How 
>>can I know when this has been fixed?
>>
>>Vicente
>>
>>
>>Lorensen, William E (Research) wrote:
>>
>>
>>
>>>As you discovered, this filter is badly broken. I've looked at the code 
>>>this morning and found a few problems already.
>>>
>>>As Karthik suggested, you should log a bug for itk at:
>>>http://www.itk.org/Bug/index.php
>>>
>>>Believe it or not, we do look at these.
>>>
>>>Bill
>>>
>>>
>>>
>>>-----Original Message-----
>>>From: insight-users-bounces+lorensen=crd.ge.com at itk.org
>>>[mailto:insight-users-bounces+lorensen=crd.ge.com at itk.org]On Behalf Of
>>>Vicente Grau
>>>Sent: Wednesday, November 30, 2005 1:07 PM
>>>To: insight-users at itk.org
>>>Subject: [Insight-users] itkGradientDifferenceImageToImageMetric
>>>
>>>
>>>I have been comparing several image-to-image metrics using a 
>>>modification of the program MeanSquaresImageMetric1.cxx. With 
>>>GradientDifferenceImageToImageMetric, I get a constant value, 
>>>independent of the translation between the images (e.g., in case of two 
>>>3D images, 40x60x60 voxels, intensity range 0-255, the value is always 339204.)
>>>I have only found an example that uses this metric, it is one of the 
>>>tests of itkAlgorithmsTests2.exe. When I run it, I get the result below. 
>>>It seems to me that this result has exactly the same problem: the same 
>>>value 20000 regardless of the translation values (and derivatives equal 
>>>to 0). Is this the expected result for this test? Is the metric working well?
>>>
>>>------------------------
>>>Available tests:
>>>...
>>>3. itkGradientDifferenceImageToImageMetricTest
>>>...
>>>To run a test, enter the test number: 3
>>>
>>>Parameters: [-50, -50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-25, -50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [0, -50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [25, -50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [50, -50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-50, -25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-25, -25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [0, -25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [25, -25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [50, -25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-50, 0], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-25, 0], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [0, 0], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [25, 0], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [50, 0], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-50, 25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-25, 25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [0, 25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [25, 25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [50, 25], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-50, 50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [-25, 50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [0, 50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [25, 50], Value: 20000, Derivatives: [0, 0]
>>>Parameters: [50, 50], Value: 20000, Derivatives: [0, 0]
>>>GradientDifferenceImageToImageMetric (0198CE00)
>>>RTTI typeinfo:   class itk::GradientDifferenceImageToImageMetric<class 
>>>itk::Image<double,2>,class itk::Image<double,2> >
>>>Reference Count: 1
>>>Modified Time: 50
>>>Debug: Off
>>>Observers:
>>>   none
>>>ComputeGradient: 1
>>>Moving Image: 0198A938
>>>Fixed  Image: 0198CAA0
>>>Gradient Image: 019C85A0
>>>Transform:    01987800
>>>Interpolator: 019C82B0
>>>FixedImageRegion: ImageRegion (0198CE54)
>>>Dimension: 2
>>>Index: [0, 0]
>>>Size: [100, 100]
>>>
>>>Moving Image Mask: 00000000
>>>Fixed Image Mask: 00000000
>>>Number of Pixels Counted: 0
>>>Test passed.
>>>
>>>
>>>_______________________________________________
>>>Insight-users mailing list
>>>Insight-users at itk.org
>>>http://www.itk.org/mailman/listinfo/insight-users
>>>
>>>
>>>
>>
>>
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