[Insight-users] Problem about LevelSetMotionRegistrationFunction

[Siwei Yang]

Jim,
thank you very much.
but I don't understand , if you want to add the current displacement 
field value to the position,   you could only derive I1(i+u, j+v) rather 
than I1(i-u, j-v) from here.

Siwei



Miller, James V (Research) wrote:

> Siwei,
>  
> The LevelSetMotionRegistrationFunction calculates the speed value as
>  
>   double speedValue = fixedValue - movingValue;
> where
>  
>   fixedValue = (double) m_FixedImage->GetPixel( index );
> and
>  
>   movingValue = m_MovingImageInterpolator->Evaluate( mappedPoint );
> where mappedPoint is calculated as
>  
>   for( j = 0; j < ImageDimension; j++ )
>     {
>     mappedPoint[j] = double( index[j] ) * m_FixedImageSpacing[j] +
>       m_FixedImageOrigin[j];
>     mappedPoint[j] += it.GetCenterPixel()[j];
>     }
>  
> In the above loop, index[] is the index of the pixel under 
> consideration in the fixed image.  By multiplying by the spacing and 
> adding the origin, the index[] is converted to a physical position in 
> the fixed image.  By adding it.GetCenterPixel(), we are adding the 
> current displacement field value to the position, i.e. (u,v). So we 
> evaluate the moving image at a position that takes into account the 
> current displacement field.
>  
> So the speed value is calculated as I1(i,j) - I2(i-u, j-v)
>  
> Does this clarify the code?
>  
> Jim
>  
>  
>  
>  
>
>     -----Original Message-----
>     *From:* Siwei Yang [mailto:s.yang at dkfz-heidelberg.de]
>     *Sent:* Friday, November 19, 2004 10:48 AM
>     *To:* insight-users at itk.org
>     *Subject:* [Insight-users] Problem about
>     LevelSetMotionRegistrationFunction
>
>     Hello all,
>     I want to use the Levelsetmotionregistrationfilter, but in the
>     ComputeUpdate (LevelsetmotionregistrationFunction) I fand
>     something doesn't seems to be comprehensible.  According to
>     equation 27 in the paper of (B.C. Vemuri, J. Ye, Y. Chen, C.M.
>     Leonard. "Image registration via level-set motion: applications to
>     atlas-based segmentation". Medical Image Analysis. Vol. 7. pp.
>     1-20. 2003.), the speed term should be     I2(ij) -I1(i-u..,
>     j-v..)    instead of  I2(ij)-I1(ij), which is in the
>     implementation.    I' m not sure, if what I say is correct .
>     Perhaps some one can give me a good answer.
>
>     Thanks
>     best wishes
>
>     Siwei Yang 
>

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