Question

Discuss the advantages and limitations of lead shielding when used for:
a) protection of the teeth and gums from a 9 MeV electron beam treating the
lower lip.
b) protection of the lens from a 6 MeV electron beam treating the lower eye lid.
c) defining the field size of an electron beam treating at 110cm SSD.

Answer 1

(a)

(b) The doses measured on the surface (cornea) and at 6 mm (lens) and 21 mm (retina) depths were all less than 5% of the maximum dose of the open field (4 x 4 cm). Electrons backscattered off a tungsten eye shield without acrylic coating increased the lid dose from 85 to 123% at 6 MeV . For the tungsten eye shield coated with 2-3 mm of dental acrylic, the lid dose was increased from 85 to 98.5% at 6 MeV.

(c)