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Re: N3 (authomatic correction of intensity in MRI data) [message #89713 is a reply to message #89705] Wed, 19 November 2014 09:41 Go to previous message
lecacheux.alain is currently offline  lecacheux.alain
Messages: 325
Registered: January 2008
Senior Member
On Tuesday, November 18, 2014 9:13:08 PM UTC+1, John K wrote:
> Hello, I'm trying to implement this algorithm in IDL.
> (papers: https://www.nitrc.org/docman/view.php/6/880/sled.pdf ; https://www.dropbox.com/s/4mmys4ikb92ya4l/original%20-%20SLE D%20John%20G.%20Sled.pdf)
> After a few weeks of researching I still have troubles understanding the b-spline smoothing.
> From what I understand it uses a TRICUBIC b-spline approximation, but I cannot find any function already implemented in IDL that can do more than a 2d spline approximation. Can anybody point me in the right direction?
> Any tips would be useful, thanks in advance.

For tricubic interpolation (which basically uses a 3D mesh of 64 data points), you may use a direct solution which involves a 64x64 matrix (product as explained by Lekien & Marsden, J.Numer.Meth.Eng., 63 (2005)), or an iterative method (refer, for instance to http://en.wikipedia.org/wiki/Tricubic_interpolation).
The latter algorithm can be coded quite easily in IDL.
Alx.
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