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| Re: N3 (authomatic correction of intensity in MRI data) [message #89706 is a reply to message #89705] |
Tue, 18 November 2014 13:24   |
rryan%stsci.edu
Messages: 16
Registered: October 2014
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Junior Member |
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On Tuesday, November 18, 2014 3:13:08 PM UTC-5, 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.
UGGH... no, but if you get it sorted out, please leave a message about what you found. I was trying to do this one day too. I know there's stuff in the IMSL library (which I don't have), but I have no idea if that supports tricubic or not.
-Russell
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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 |
lecacheux.alain
Messages: 325
Registered: January 2008
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Senior Member |
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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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