dicomread() not handling negative values properly

I am using the "dicomread" function to read in a DICOM file. The function seems to be converting all my negative values to zero which then shows a black spot at those points when it is extracted to an image.

>> x = dicomread(filename)

How do I fix this?

Answer 1

[MathWorks Support Team]

This is occurring because MATLAB is reading the DICOM as unsigned integers. This can be seen by looking at the output of the "dicominfo" function.

>> info = dicominfo(filename)

The 'PixelRepresentation' shows 0 when the DICOM is unsigned and 1 when the DICOM is signed.

In order to get the desired values back, simply use the following equation to do a linear rescaling.

>> y = int16(x) *info.RescaleSlope + info.RescaleIntercept