The surface doses from orthovoltage x-ray treatments

Measurements have been made of the surface dose with treatment cones and lead shielding used with orthovoltage x-ray systems. Both devices significantly increase the surface dose, probably by the generation of photoelectrons. The surface dose depends upon the shape and material of the cone and the x-ray energy. The surface dose can be 500% higher than the dose measured with a Baldwin-Farmer chamber. The significance of these doses is discussed in the light of recent information on the thickness of the epithelium. It is suggested that every effort be made to reduce the surface dose by using low atomic number material between the lead and the patient surface.