Sir this data set is for brain, you have to first install microdicom software 32 or 64 bit according to your system and then they will open I am adding a paper from which you can get information about the data provider, latest version of paper is uploaded on IEEE explorer.
It contains manual segmentation of left and right parotid glands, brainstem, optic chiasm, optic nerves (both left and right), mandible, submandibular glands (both left and right) and manual identification of bony landmarks.