Use dicomInfo and imref3d to create a mask of a dicomContours object.

Read the metadata of a DICOM-RT Structure Set.

info = dicominfo('rtstruct.dcm');

Construct a dicomContours object.

rtContours = dicomContours(info);  

Display all the ROI information as a table.

rtContours.ROIs

ans=2×5 table
    Number          Name           ContourData    GeometricType       Color    
    ______    _________________    ___________    _____________    ____________

      1       {'Body_Contour' }    {90×1 cell}     {90×1 cell}     {3×1 double}
      2       {'Tumor_Contour'}    {21×1 cell}     {21×1 cell}     {3×1 double}

Plot the contours of all ROIs using plotContours. This object function plots the contours in world coordinates. Use this plot to define world coordinate limit boundaries for an imref3d object to create a dense mask within.

plotContour(rtContours)

Create an imref3d object with same world limits as the plot from plotContours so that the image is in the same space as the contours.

referenceInfo = imref3d([128,128,50],xlim,ylim,zlim);

Create a 3-D logical mask of the first contour ('Body_Contour') in the rtContours. Specify the imref3d object

contourIndex = 1;  
rtMask = createMask(rtContours, contourIndex, referenceInfo);

View this mask using the Volume Viewer

volshow(rtMask);