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sum pixel value in an image.

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Hi all,
I have a series of images in one dicom file (n =16 images). How can i find frames that contain maximum and minimum sum of pixel values (i.e. signals) and how to find their corresponding values (i.e. the sum of pixel values for the maximum frame and minimum frame) ?
the file is called MUGA.dcm

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Accepted Answer

Divya Yerraguntla
Divya Yerraguntla on 23 Sep 2019
Hi Ahmad,
Try using the following code to find the sum of pixels of images in DICOM file.
n=[];
% Find sum of images by providing your DICOM file name
for i=1:10
[X, map] = dicomread('DICOM filename','frames',i);
n = [n,sum(X(:))];
end
% Find maximum and minimum summation and indices.
[min, minidx] = min(n);
[max, maxidx] = max(n);
Hope it helps!

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Ahmad Alenezi
Ahmad Alenezi on 25 Sep 2019
Hi Divya
Does this find the pixel values (signals) of pixel count ?
And how to find that which frame got the highest values ?
And what does 'frames' indicate for ?
Best, Ahmad

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More Answers (3)

Divya Yerraguntla
Divya Yerraguntla on 27 Sep 2019
Hi Ahmad,
  1. Yes, the dicomread function returns the pixel values of the file and stores it in variable X in the above mentioned code.
  2. The variable maxidx in the above code gives the frame number which has the maximum pixel sum value and variable max gives the pixel sum of that frame.
  3. 'frames' indicates the frames to read, specified as an integer scalar, a vector of integers, or 'all'. When value of 'frames' is numeric, dicomread reads only the specified frame numbers from the image. By default, dicomread reads all frames of the DICOM image.
Have a look at dicomread for more information on the function.
Hope it helps!

  3 Comments

Ahmad Alenezi
Ahmad Alenezi on 27 Sep 2019
Thank you for you reply.
the code is giving me the following results.
i = 16
max = 5027636
maxidX = 1
min = 5027636
minidX = 1
These results are not expected !
do you know what could be the problem ?
i used the code as below:
n=[];
% Find sum of images by providing your DICOM file name
for i=1:16
[X, map] = dicomread('MUGA.dcm','frames',i);
n = [n,sum(X(:))];
end
% Find maximum and minimum summation and indices.
[min, minidx] = min(n);
[max, maxidx] = max(n);
Divya Yerraguntla
Divya Yerraguntla on 27 Sep 2019
Could you provide MUCA.dcm file?
Ahmad Alenezi
Ahmad Alenezi on 30 Sep 2019
This is the file.
Thanks.

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Divya Yerraguntla
Divya Yerraguntla on 4 Oct 2019
Hi Ahmad,
The code and file you have provided are giving the following results.
Dicom-Workspace.PNG
Are these the expected ones?

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Ahmad Alenezi
Ahmad Alenezi on 4 Oct 2019
Hi Divya,
Yes, these results are the expected. Thanks indeed
One last question:
I know how to apply region of interest over a small part of the image (see image). This results in 128x128x16 uint 16 array (I call it ROI). How can I put ROI instead of dicomread('MUGA.dcm').?? meaning that i want my input to be ROI instead of MUGA.dcm
roi muga.png
Best,
Ahmad

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Subhadeep Koley
Subhadeep Koley on 4 Nov 2019
Ahmad, the code is running in my end without any error. I am using the the attached DICOM file.
Subhadeep Koley
Subhadeep Koley on 4 Nov 2019
I think the DICOM file you are using has less than 16 channels.
However, please use the code below. It is more generalized and will work for DICOM files of any channel length.
clear;close all;clc;
X = rescale(squeeze(dicomread('MUGA1.dcm'))); % Read your DICOM
temp = rescale(X(:,:,1)); % Select one frame from the mask generation
mask = roipoly(temp); % Specify polygon ROI with the interactive polygon selection tool
X_masked = zeros(size(X)); n = [];
for i=1:size(X,3)
for j=1:128
for k=1:128
if(mask(j,k) == 1)
X_masked(j,k,i) = X(j,k,i);
n = [n,sum(X_masked(:))];
end
end
end
end
% Find maximum and minimum summation and indices.
[minVal, minIdx] = min(n);
[maxVal, maxIdx] = max(n);
Hope this helps!

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