In this report the history of shielding for radiation treatment rooms
is traced from the time of the discovery of x rays to the present. Dur
ing the early part of the twentieth century the hazards from ionizing
radiation were recognized and the use of lead and other materials beca
me commonplace for shielding against x rays. Techniques for the calcul
ation of the shield thickness needed for x-ray protection were develop
ed in the 1920's and shielding materials were characterized in terms o
f the half value layer or simple exponential factors. At the same time
, better knowledge of the interaction between radiation and matter was
acquired. With the development of high energy medical accelerators af
ter 1940, new and more complex shielding problems had to be addressed.
Recently, shielding requirements have become more stringent as standa
rds for exposure of personnel and the general public have been reduced
. The art of shielding of radiation treatment facilities is still bein
g developed and the need for a revision of the reports on shielding of
medical accelerators from the National Council on Radiation Protectio
n and Measurements is emphasized in this article.