# I am a beginner of using matlab. I have a extracted ROI of lung CT scan. I want to remove the rod (stick) like structures from that binary image in order to left only the round objects ( nodules). Please, kindly advise me.

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May on 26 Jan 2017
Commented: Takuji Fukumoto on 26 Jan 2017
%%Checking Round
[B,L]=bwboundaries(bw,'noholes');
imshow(L);
% imshow(label2rgb(L, @jet, [.5 .5 .5]));
hold on
% for k = 1:length(B)
% boundary = B{k};
% plot(boundary(:,2), boundary(:,1), 'w', 'LineWidth', 2);
% end
stats= regionprops(L,'Area','Centroid');
% threshold= 0.94;
% loop over the boundaries
for k=1:length(B)
% obtain (X,Y) boundary coordinates corresponding to label 'k'
boundary=B{k};
% compute a simple estimate of the object's perimeterd
delta_sq= diff(boundary).^2;
perimeter= sum(sqrt(sum(delta_sq,2)));
%obtain the area calculation corresponding to label 'k'
area = stats (k).Area;
%compute the roundness metric
metric = 4*pi*area/perimeter^2;
%display the results
metric_string = sprintf('%2.2f',metric);
% mark objects above the threshold with a black circle
if metric > 0.5
% text(boundary(1,2)-35,boundary(1,1)+13,metric_string,'Color','y',...
% 'FontSize',13,'FontWeight','bold');
% centroid = stats(k).Centroid;
% plot(centroid(1),centroid(2),'ko');
end
% text(boundary(1,2)-35,boundary(1,1)+13,metric_string,'Color','y',...
% 'FontSize',13,'FontWeight','bold');
end

Takuji Fukumoto on 26 Jan 2017
I recommend you to use regionprops function. You can measure properties of binary image with this.
stats = regionprops(BW,'Eccentricity')
The eccentricity is the ratio of the distance between the foci of the ellipse and its major axis length. The value is between 0 and 1. (0 and 1 are degenerate cases. An ellipse whose eccentricity is 0 is actually a circle, while an ellipse whose eccentricity is 1 is a line segment.)
You can identify the round objects if you choose the BWs whose eccentricity value is small.
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Takuji Fukumoto on 26 Jan 2017
Here is command.
BW = imbinarize(rgb2gray(I));
BW_out = bwpropfilt(BW, 'Eccentricity', [0.5, 1]);
figure ,imshow(BW_out);
I think eccentricity of all region is greater than 0.7.
And type this command on MATLAB.
imageRegionAnalyzer
This application make it easy to analyze and filter regions by properties.