DICOM Images show greyish

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Simon
Simon am 25 Okt. 2021
Kommentiert: Simon am 26 Okt. 2021
Hi there,
im curently working with CT and MRI Scans in DICOM Format. The MRI Images work completly fine, but the CT Images look this greyish. It is the same in the matlab Dicom Viewer but not in Online Viewers, there the Images are shown normal.
I already tried to rescale them, but it didn't help at all?
Has anybody an Idea where this comes from and how to fix it?
Thanks for your help :)
  7 Kommentare
DGM
DGM am 25 Okt. 2021
Bearbeitet: DGM am 25 Okt. 2021
It depends what you mean by changing the contrast. The above example does increase the contrast.
A = rgb2gray(imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/777493/image.jpeg'));
range(double(A(:)))/mean(double(A(:))) % example contrast metric
ans = 1.2804
A = mat2gray(A,double([mode(A(1,:)) max(A(:))]));
range(double(A(:)))/mean(double(A(:))) % check contrast again
ans = 12.5577
imadjust will let you adjust input and output black/white points (linear) and optionally adjust gamma. stretchlim() can be used for finding the values needed by imadjust(). I'm sure there are other things that can be done too, depending on what you need. Phrases like "contrast adjustment" or "contrast enhancement" are unfortunately kind of vague, since they can mean contradictory things in different contexts.
Simon
Simon am 25 Okt. 2021
Thank you guys for all your help, so far im a a state, where I can continue in processing ;)

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Antworten (2)

Image Analyst
Image Analyst am 25 Okt. 2021
Try using [] in imshow() to scale your min to 0 and max to 255:
imshow(yourGrayScaleImage, []);
  21 Kommentare
Image Analyst
Image Analyst am 26 Okt. 2021
OK since the reconstruction diameter is 500 for one of the images, and the image is 512x512 for both images, what is the reconstruction diameter for the other image? If the discs are the same size in the real world then the cm per pixel spatial calibration factor must be different for the two images because the discs shows up with a different pixel diameter in the two images.
Simon
Simon am 26 Okt. 2021
Just for understanding, here you can see what these two discs originally looked like. (The right one is changed to binary already, cause of the original problem)
Also the left Image is saved as 256x256

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Simon
Simon am 26 Okt. 2021

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