Equalize grayscale of two dicom images and subtract

Hi,

I want to compare two dicom images, see figures below. I want to know whether there is a difference in size between the two 'circles'. To visualize this, I want to subtract the two images to see if a 'ring' remains (something like the figure below).

However the problem is that the two dicom images have a different grayscale. So therefore I first have to equalize the two grayscales. After that I can subtract the two images (I think...?).

I hope I explained clearly what I want to achieve, I am quite new to matlab. Hope someone can help. Thanks!!

Answer 1

[Priysha LNU]

Hi,

You may use 'dicomread()' MATLAB function to read both image files into MATLAB. For detailed information of this function, you may refer to the following documentation link:

https://www.mathworks.com/help/images/ref/dicomread.html

Read both images as:

Im1 = dicomread('Fig1.dcm');
Im2 = dicomread('Fig2.dcm');

Having read both the image files, you can then display the difference in images by:

imshow(Im2 - Im1);

This will show a single image with difference in pixels of the two input images.

You can also display following different types of errors in MATLAB:

(Im2 - Im1)    % Errors
(Im2 - Im1).^2   % Squared Error
mean((Im2 - Im1).^2)   % Mean Squared Error
RMSE = sqrt(mean((Im2 - Im1).^2));  % Root Mean Squared Error

Hope this helps!

DISCLAIMER: These are my own views and in no way depict those of MathWorks.

[Tain Neupane]

Hi Priysha,

I am wondering if you have a folder with multiple dicom images (like CT/PET slices), how do you compare ? I mean how do you loop in? I need help with this! Thank you in advance!

-Tain

[Image Analyst]

@Tain Neupane, see the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_process_a_sequence_of_files?