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73 lines
3.8 KiB
Matlab
73 lines
3.8 KiB
Matlab
% INVERT_DVF simple iterative method for estimation of the inverse deformation
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% field
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% Chen, Mingli, et al. "A simple fixed‐point approach to invert a deformation field a." Medical physics 35.1 (2008): 81-88.
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%
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% [deform_tensors,inv_deform_tensors] = invert_DVF(deform_tensors, Npix_vol)
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%
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% **deform_tensors cell of 3D arrays containing forward deformation DVF
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% **Npix_vol pixel size of the recosntructed volume
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% Outputs:
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% ++deform_tensors_linear calculate forward DVF
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% ++inv_deform_tensors_linear calculate inverse DVF
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%*-----------------------------------------------------------------------*
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%| |
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%| Except where otherwise noted, this work is licensed under a |
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%| Creative Commons Attribution-NonCommercial-ShareAlike 4.0 |
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%| International (CC BY-NC-SA 4.0) license. |
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%| |
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%| Copyright (c) 2018 by Paul Scherrer Institute (http://www.psi.ch) |
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%| |
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%| Author: CXS group, PSI |
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%*-----------------------------------------------------------------------*
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% You may use this code with the following provisions:
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%
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% If the code is fully or partially redistributed, or rewritten in another
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% computing language this notice should be included in the redistribution.
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%
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% If this code, or subfunctions or parts of it, is used for research in a
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% publication or if it is fully or partially rewritten for another
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% computing language the authors and institution should be acknowledged
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% in written form in the publication: “Data processing was carried out
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% using the “cSAXS matlab package” developed by the CXS group,
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% Paul Scherrer Institut, Switzerland.”
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% Variations on the latter text can be incorporated upon discussion with
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% the CXS group if needed to more specifically reflect the use of the package
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% for the published work.
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%
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% A publication that focuses on describing features, or parameters, that
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% are already existing in the code should be first discussed with the
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% authors.
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%
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% This code and subroutines are part of a continuous development, they
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% are provided “as they are” without guarantees or liability on part
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% of PSI or the authors. It is the user responsibility to ensure its
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% proper use and the correctness of the results.
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function [deform_tensors,inv_deform_tensors] = invert_DVF(deform_tensors, Npix_vol)
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Niter = 10;
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%% find invert transformation
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N = length(deform_tensors);
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for block = 1:N
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% init guess
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for ax = 1:3
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inv_deform_tensors{block}{ax} = -deform_tensors{block}{ax};
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end
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for i = 1:Niter
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for ax = 1:3
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scale = size(deform_tensors{block}{ax}, ax) / Npix_vol(ax) ; % calculate the deformation in deform_tensors grid
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inv_deform_tensors{block}{ax} = inv_deform_tensors{block}{ax}*0.5 + 0.5*utils.interp3_gpu(-deform_tensors{block}{ax}, ...
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scale*inv_deform_tensors{block}{1},scale*inv_deform_tensors{block}{2},scale*inv_deform_tensors{block}{3});
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end
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end
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% in my code I assume that deform_tensors and inv_deform_tensors
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% have the same direction (in the astra the direction is swapped)
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for ax = 1:3
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inv_deform_tensors{block}{ax} = -gather(inv_deform_tensors{block}{ax});
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end
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end
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end
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