Support:Documents:Examples: Reslicing using COMKAT image tool (advanced)

Reslicing 3D image using COMKAT image tool

Overview

Reslicing a 3D image dataset can be accomplished using the COMKAT image tool and sliceVolume(). This example explains how to obtain resliced 3D images using COMKAT image tool.

Step 1.

Load a file using COMKAT image tool and use the functions to translate and rotate the image volume as you desire.

Step 2.

Send the GUI handles of COMKAT image tool to MATLAB workspace.

Step 3.

Create following MATLAB function:

function outputVolume = fcnReSlice(GUI_handles, a_row, a_column, a_plane, flagUseCurrIvd)
%%*****************************************************************************************%%
% Example:  Using ImageVolumeData::sliceVolume() to reslice 3D images
% e.g. 
%  outputVolume = fcnReSlice(GUI_handles [, a_row, a_column, a_plane, flagUseCurrIvd]);
% 
%  Parameters -
%      GUI_handles : GUI handles obtained from comkatimagetool
%            a_row : Desired aspect ratio in row direction     (default: 1.0)
%         a_column : Desired aspect ratio in colume direction  (default: 1.0)
%          a_plane : Desired aspect ratio in plane direction   (default: 1.0)
%   flagUseCurrIvd : A flag to control the data used to reslice 
%                    ( 1: Current COMKAT ImageVolumeData (default), 0: Original)
%     outputVolume : Resliced 3D volume images
%
%
%   Dylan Su  2012-07-30
%   kuan-hao.su@case.edu
%%*****************************************************************************************%%

%% Obtain the imageVolumeData object from GUI_handles
ivd = GUI_handles.imageVolumeData{1}; % assume PET is image 1

if nargin == 1,
    a_row = 1;
    a_column = 1;
    a_plane = 1;
end

if nargin < 5,
    flagUseCurrIvd = 1;  % 1: use current COMKAT image volume
end

if (~flagUseCurrIvd),
    %% Get the information from origianl data
    positionInput = get(ivd,'ImagePositionPatient');
    orientationInput = get(ivd,'ImageOrientationPatient');
    pixelSpacing = get(ivd, 'PixelSpacing');
    [nr, nc, np, ~] = get(ivd, 'VolumeDimension');
    nrows = nr;
    ncols = nc;
    nplanes = np;
    
else
    %% Get the information from current COMKAT imageVolumeData
    idxSA = 1;  % get infor from short axis (SA) view
    
    positionInput = GUI_handles.view{idxSA}.position{1};
    orientationInput = GUI_handles.view{idxSA}.orientation{1};
    pixelSpacing = repmat( GUI_handles.view{idxSA}.pixelSpacing(1),[1,3]);
    nrows = GUI_handles.rows;
    ncols = GUI_handles.columns;
    
    [~, ~, np, ~] = get(ivd, 'VolumeDimension');
    
    pixelSpacingOrg = get(ivd, 'PixelSpacing');
    
    nplanes = ceil(np * pixelSpacingOrg(3) / pixelSpacing(3)); 
end

%% Calculate the desired dimension
dnrows = ceil(nrows * a_row);
dncols = ceil(ncols * a_column);
dnplanes = ceil(nplanes * a_plane);

% calcualte new pixelSpacing by preserving the original FOV size
pixelSpacing = pixelSpacing ./ [dnrows/nrows, dncols/ncols, dnplanes/nplanes];

%% Set the scale and offset the same as the original volume
% use same scale and offset for subvolume as original volume
% 0 = scaledPixel = rawPixel * s + o --> rawPixel = -o/s;
s = get(ivd, 'VolumeFrameBufferScaleFactor');
o = get(ivd, 'VolumeFrameBufferRescaleIntercept');

rawBackgroundPixelValue = -o/s;

%% Determine location of first pixel in output volume
posSA = positionInput;

% xyz of the center of first pixel
if (~flagUseCurrIvd),
    % for subject's data, 'posSA' is the center of the first pixel
    position = posSA;
else
    % for imageVolumeData, 'posSA' is the center of the folume
    position = posSA - orientationInput(:,3) * (dnplanes * pixelSpacing(3)) / 2;
end

planePosStep = orientationInput(:,3) * pixelSpacing(3); % calculate the step of new plane position

%% Build output volume plane-by-plane
outputVolume = zeros(dnrows, dncols, dnplanes);  % initialize the output images

for idxP = 1 : dnplanes,
    planePos = position + (idxP - 1) * planePosStep; % position of plane to be interpolated
    
    % determine indicies in original volume corresponding to xyz physical (mm) location of plane
    [u, v, w] = coordinateGen(ivd, ...
        dncols, dnrows, pixelSpacing, planePos, orientationInput);
    
    % obtain a slice by interpolating from the ivd volumeFrameBuffer
    fprintf('plane ==> %i/%i\n', idxP, dnplanes);
    outputVolume(:, :, idxP) = sliceVolume(ivd, v , u , w, rawBackgroundPixelValue,'linear');
    
end