[Insight-users] Computing the metric value?

[motes motes]

In the itkSoftwareGuide page 415 it says:

"In ITK, itk::ImageToImageMetric objects quantitatively measure how
well the transformed moving
image fits the fixed image by comparing the gray-scale intensity of the images."


I don't understand the term "transformed moving image". As I
understand the moving image is never transformed.
Actually its the pixels in the fixed image that is transformed based
on the following steps in the metric:


1) First the intensity value of the current point in the fixed image
is looked up:

                      fixedValue = I(Fp)

2) Next the current point in the fixed image is transformed using the
current parameters:

                     transformedPoint = T(Fp)

3) Now this transformed point is feed to the interpolator connected to
the moving image:

                     movingValue =
movingImage->interpolator->Eval(transformedPoint)

4) The difference:

                     diff += movingValue - fixedValue

is computed.


Therefore the sentence from the itkSoftwareGuide to my understand should be:

"In ITK, itk::ImageToImageMetric objects quantitatively measure how
well the intensity
in the moving image at the transformed fixed coordinates fits the
intensity in the non-transformed
fixed image by comparing the gray-scale intensity of the images."

Or am I missing the point here?






In the image registration method the metric is used to compare how
identical the fixed image is with the tr