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.
Wegener WA, Alavi A.Wegener WA, et al.Int J Rad Appl Instrum B. 1991;18(6):569-82. doi: 10.1016/0883-2897(91)90027-i.Int J Rad Appl Instrum B. 1991.PMID: 1743981Review.