Is it possible to imwrite only the contents of particle boundary?

Hi all - My overall aim is to segment these particles from each other and export only the particle images for further analysis. So far I have;

Successfully thresholded the image, overlayed binary mask on original image, labelled each particle & determined the boundary for each.

Now I would like to separate each particle from each other and create separate images of only the particle and nothing else outside of the boundaries. I have only been able to find methods for drawing a rectangle around each the extremities of particle and using this.

Any help would be greatly appreciated!

Many thanks,

Joe

boundaries = bwboundaries(binaryImage);
numberOfBoundaries = size(boundaries, 1);
for k = 1 : numberOfBoundaries
    thisBoundary = boundaries{k};
    plot(thisBoundary(:,2), thisBoundary(:,1), 'g', 'LineWidth', 2);
end