I'm trying to display each dicom file like the left panel in the picture below:

(source : https://www.dicomlibrary.com)
But I just can display the black squares like this, for example, I choose 4 dicom files, so 4 blacks squares were created.

So how can I display the image inside the square? Maybe it relates to the the camera and the scene, but I don't know how to make it. Can anybody help me? Thank you a lot!