Certain Data Elements are no longer supported beginning with Version 3.0 of this standard. These Data Elements are retired and are denoted as such (RET) in the VR column in PS 3.6 of the DICOM Standard. Implementations may continue to support these Data Elements for the purpose of backward compatibility with versions of the standard prior to V3.0, but this is not a requirement of the standard. If a retired Data Element is used it must contain valid data as specified in versions of the standard prior to V3.0. Any other use of a retired Data Element, and its associated Data Element Tag, is reserved by the standard. Retired Data Element Tags shall not be redefined in later versions of the standard.