how to extract list image using point (reatangle) means four points

Hi Everyone

if i want list of pixel value that i have some point (ractangle)

let say i want list of pixel value from 58:71 58:74 85:75 90:60 71:71 (rectangle area), how to write the code?

this is my old code:

a = dicomread('I10.dcm' );
mask = (a >= 800) & (a <= 850);
for sliceIndex = 1 : size(a, 3)
    % Get 2-D mask at this slice level.
    thisMask = mask(:,:,sliceIndex);
    % Extract rows and columns for this slice only, not all of them.
    [rows, columns] = find(thisMask); 
    % Etc.  Now add these rows and columns to a master list of them over all slices.  (You do this)...
end