Cadmium free lead alloy for reusable radiotherapy shielding.

A low melting point cadmium free fusible lead alloy suitable for custom radiotherapy shielding blocks is described. The alloy, referred to here as Alloy-203, differs in composition from the more common Lipowitz's metal (Cerrobend) by being cadmium free, having a slightly higher lead content and a 203 degrees F melting temperature. Attenuation properties have been studied for 4-18 MV X-rays. Alloy-203 has lower transmission than Lipowitz's metal, primarily due to the higher content of lead and bismuth. Daily use for the past 2 years at Mayo Clinic has not indicated any major problems associated with the use of this cadmium free alloy for custom shield fabrication.