MR Segmentation to draw marker over the MR Dicom Images
Typically research papers handling DICOM standard images would probably extract the ROI using pixel processing methods. However, a lot of medical imaging companies like to implement their own DICOM tags(public/private) to keep track of such information for various purposes.

For example, General Electric keeps the following tag enabled on most MR images:

VerticesOfTheRegion found at (0028,9503), which is according to the DICOM standard, a private tag(odd location tags are private)

In short: Its implausible to tell you,how was the ROI extracted without having access to the DICOM metadata of the image in question.