Detect boudary of volume

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Hugo
Hugo 2013-12-30
回答： Image Analyst 2013-12-30
Hi all,
I am trying to create a 3D ROI/Area of the outer boundary from a MRI scan of the Head neck region. Therefore i made it a logical volume and created a code that detects the first and last one in each row and column. But as you might would expect there are some gaps in this boundary which i would like to close. (in other words i want to connect the found coordinates to each other). Can anybody tell me how to do this?
I will place an example image under my code, this is the code i use to detect the boundary:
if true
%
z = size (MRIt);
for j = 1: z(3);
A = squeeze (MRIt(:,:,j));
[row column] = size(A);
Edge = row * zeros(row, column);
Edge1 = row * zeros(row, column);
for i = 1:row;
B = A(i,1:end);
[x,y] = find (B, 1, 'first');
Edge(i,y)= 1 ;
end
for i = 1:row;
B = A(i,1:end);
[x,y] = find (B, 1, 'last');
Edge(i,y)= 1 ;
end
for i = 1:column;
B = A(1:end,i);
[x,y] = find (B, 1, 'first');
Edge(x,i)= 1 ;
end
for i = 1:column;
B = A(1:end,i);
[x,y] = find (B, 1, 'last');
Edge(x,i)= 1 ;
end
MRIe(:,:,j) = Edge;
end
end

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回答（2 个）

Walter Roberson
Walter Roberson 2013-12-30
Consider using "morphological closing", http://www.mathworks.com/help/images/ref/bwmorph.html . This would be "dilating" the existing pixels until they flow together to fill the gaps, then eroding back to give you the continuous outline.
Image Analyst
Image Analyst 2013-12-30
You don't want to do it like that. Get rid of all those loops over rows and columns - they're no good as you've already found out. What you should do, if you want to create a binary "shell" of the skull is to call bwperim and assign that to MRIe:
for j = 1: z(3);
A = MRIt(:,:,j) > 0;
MRIe(:,:,j) = bwperim(A);
end

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