If I understand your question correctly, you would like to import a file that has been stored in Dicom format into ROOT. I assume to further analyze/manipulate the data with the existing ROOT tools .
Of course that is possible, however ROOT does not contain the necessary software to read/interpret the Dicom format but it is possible by linking it to the package DCMTK (OFFIS DICOM Toolkit) ; it contains the header file
#include "DicomImage.h"
in dcmimgle: an image processing library and utility apps
If after loading your image into ROOT, you use only the DCMTK tools, there is no point loading it into ROOT.
In order to access the DCMTK functionality in ROOT, your “include” statement is not enough but many people on this Forum can guide you through the steps.
-Eddy
ps. I see here a post from 2011 where somebody tried to access Dicom file using Python and manipulate it further in ROOT. Looking here I see that there are now many options in Python to access the Dicom data.