An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Cornford E, Twining P.Cornford E, et al. Among authors: twining p.Clin Radiol. 1992 Mar;45(3):172-4. doi: 10.1016/s0009-9260(05)80634-8.Clin Radiol. 1992.PMID: 1555367