CT slices appear with different intensity

Hi!

I have a problem with some rabbit CT-s.

When I import them to matlab with dicomread, some of the slices have increased or decreased intensity for the same tissue structure.

However if I open the same set of iamges in DICOM viewer, it looks normal.

How can I address this?

Answer 1

[Miklos Kassai]

I found the solution with some help from colleagues.

There is two value in the CT metadata: RescaleSlope and RescaleIntercept.

To receive the HU values, you have to multiply the array values with the RescaleSlope and add RescaleIntercept.

It turns out, my CT-s had different RescaleSlope and RescaleIntercept values for each and every slice, therefore I had to apply the equation for every slice.

The CT filenames spread from 0000 to 0511.

Sorry for the very basic code, I'm sure it has a lot of unnecessary parts but it works for me.

ximgrescd=zeros(512,512,512); 
            
     for j=1:9
       dicomFileName=strcat('CT-000',num2str(j),'.dcm')
       ximglayer=dicomread(dicomFileName)
       info=dicominfo(dicomFileName)
       
       ximgrescd(:,:,j) = ximglayer * info.RescaleSlope + info.RescaleIntercept;
     end
     
     
     for j=10:99
       dicomFileName=strcat('CT-00',num2str(j),'.dcm')
       ximglayer=dicomread(dicomFileName)
       info=dicominfo(dicomFileName)
       
       ximgrescd(:,:,j) = ximglayer * info.RescaleSlope + info.RescaleIntercept;
     end
    
    
     for j=100:511
       dicomFileName=strcat('CT-0',num2str(j),'.dcm')
       ximglayer=dicomread(dicomFileName)
       info=dicominfo(dicomFileName)
       
       ximgrescd(:,:,j) = ximglayer * info.RescaleSlope + info.RescaleIntercept;
     end