EFFECT OF LEAD SHIELDING CUTOUTS ON DOSE TO OVERLYING TISSUE FOR 7 MV ELECTRONS

Abstract Treatment of the helix of the ear with a lead shield placed behind the ear during electron beam therapy significantly increases the radiation close to the skin above the block. With film densitometry, the increased radiation dose is 10 % higher than the dose at the dose maximum. It is believed that the increase is a result of bremssrrahlung and scattered electrons originating in the lead. The increased dose should be taken into account when calculating the dose to those structures.